Question 1

Recognize uniform decimal scaling in sums of squares: Compute [(0.05)^2 + (0.41)^2 + (0.073)^2] / [(0.005)^2 + (0.041)^2 + (0.0073)^2] using powers-of-10 relationships.

Accepted Answer

Introduction / Context: This problem checks whether you can see patterns in decimal scaling. The denominator terms are each precisely one-tenth of the corresponding numerator terms, and squaring magnifies that scaling in a predictable way. Exploiting this pattern yields the answer instantly. Given Data / Assumptions: Numerator: (0.05)^2 + (0.41)^2 + (0.073)^2. Denominator: (0.005)^2 + (0.041)^2 + (0.0073)^2. Concept / Approach: If x is scaled to x/10, then (x/10)^2 = x^2/100. Since every denominator term is the square of a numerator term divided by 10, each denominator square equals the corresponding numerator square divided by 100. Thus the whole denominator is 1/100 of the numerator sum, and the ratio is 100. Step-by-Step Solution: Observe: 0.005 = 0.05/10; 0.041 = 0.41/10; 0.0073 = 0.073/10.Therefore: (0.005)^2 = (0.05)^2/100, etc.Sum of denominator squares = (sum of numerator squares)/100.Hence overall ratio = (Numerator) / (Numerator/100) = 100. Verification / Alternative check: Pick one pair to test: (0.05)^2 = 0.0025; (0.005)^2 = 0.000025; indeed a factor of 1/100. Why Other Options Are Wrong: 0.1, 10, 1000: Each assumes an incorrect scaling factor (1/10, 10, or 1000) rather than 100. Common Pitfalls: Forgetting that the square of a tenth is a hundredth. Adding before recognizing the uniform scaling wastes time and risks arithmetic slips. Final Answer: 100

Question 2

Use a^2 − b^2 factorization with decimals: Evaluate 13.065^2 − 3.065^2 by rewriting it as (a − b)(a + b) and computing quickly.

Accepted Answer

Introduction / Context: The classic identity a^2 − b^2 = (a − b)(a + b) is a powerful shortcut, especially with decimals. It replaces squaring and subtracting with two additions/subtractions and one multiplication, greatly reducing error likelihood and saving time. Given Data / Assumptions: a = 13.065, b = 3.065. Compute a^2 − b^2. Concept / Approach: Apply a^2 − b^2 = (a − b)(a + b). The numbers are chosen so that a − b is an integer, making the product particularly simple to evaluate accurately. Step-by-Step Solution: a − b = 13.065 − 3.065 = 10.000.a + b = 13.065 + 3.065 = 16.130.Therefore a^2 − b^2 = (a − b)(a + b) = 10.000 × 16.130 = 161.3. Verification / Alternative check: Rough check: 13^2 − 3^2 = 169 − 9 = 160, near 161.3, consistent with decimal offsets. Why Other Options Are Wrong: 159.5 and 141.6: Result from mis-adding a + b or misplacing decimals. 100: Confuses a^2 − b^2 with (a − b)^2 or only takes a − b. Common Pitfalls: Losing decimal places during addition. Attempting the full squaring, increasing arithmetic risk. Final Answer: 161.3

Question 3

Factor common terms in numerator and denominator: Evaluate (.896 × .752 + .896 × .248) / (.7 × .034 + .7 × .966) by factoring and simplifying before dividing.

Accepted Answer

Introduction / Context: Before multiplying decimals, look for common factors you can pull out. This problem is designed for factoring: both the numerator terms have a common 0.896 and the denominator terms have a common 0.7. Recognizing this pattern turns a messy quotient into a simple ratio. Given Data / Assumptions: Numerator: 0.896 × 0.752 + 0.896 × 0.248. Denominator: 0.7 × 0.034 + 0.7 × 0.966. Concept / Approach: Use distributive factoring a×x + a×y = a(x + y). In both numerator and denominator, the bracketed sums equal 1. This observation reduces the whole fraction to the ratio of the common factors 0.896 to 0.7, which is quick to compute. Step-by-Step Solution: Numerator: 0.896(0.752 + 0.248) = 0.896 × 1 = 0.896.Denominator: 0.7(0.034 + 0.966) = 0.7 × 1 = 0.7.Quotient = 0.896 / 0.7 = 1.28. Verification / Alternative check: Multiply top and bottom by 1000 to clear decimals: 896 / 700 = 128 / 100 = 1.28. Why Other Options Are Wrong: 0.976: Comes from dividing 0.896 by 0.918 or other mis-summed bracket. 12.8 and 9.76: Lose track of decimal places (×10 or ×100 too much). Common Pitfalls: Multiplying terms directly instead of factoring first. Mistallying 0.034 + 0.966 to something other than 1. Final Answer: 1.28

Question 4

Evaluate using identities and exact arithmetic: Compute (.356 × .365 − 2 × .365 × .106 + .106 × .106) / (.632 × .632 + 2 × .632 × .368 + .368 × .368) without rounding until the end.

Accepted Answer

Introduction / Context: This fraction features two classic algebraic patterns hidden in decimal arithmetic. The denominator is of the form x^2 + 2xy + y^2 = (x + y)^2, which collapses neatly. The numerator resembles a squared-expression expansion but with mixed products, so computing it exactly is prudent. The exercise builds precision and pattern recognition. Given Data / Assumptions: Numerator: 0.356 × 0.365 − 2 × 0.365 × 0.106 + 0.106 × 0.106. Denominator: 0.632 × 0.632 + 2 × 0.632 × 0.368 + 0.368 × 0.368. Compute the exact decimal value and then simplify the ratio. Concept / Approach: First, simplify the denominator using the identity (x + y)^2. Here x = 0.632 and y = 0.368, so x + y = 1, hence denominator = 1^2 = 1. Next, compute the numerator by careful multiplication and combination of terms. No further identity fully collapses the numerator because the first term is a product of two different decimals (0.356 and 0.365). Step-by-Step Solution: Denominator: (0.632 + 0.368)^2 = 1^2 = 1.Compute 0.356 × 0.365 = 0.129940.Compute 2 × 0.365 × 0.106 = 2 × 0.038690 = 0.077380.Compute 0.106 × 0.106 = 0.011236.Numerator = 0.129940 − 0.077380 + 0.011236 = 0.063796 ≈ 0.0638.Since denominator = 1, the overall value is 0.063796 ≈ 0.0638. Verification / Alternative check: Estimate bounds: 0.356 × 0.365 ≈ 0.13; subtract ~0.077 and add ~0.011 gives near 0.064, confirming the computation. Why Other Options Are Wrong: 0.0765 and 0.345: Result from mis-multiplying or mis-subtracting terms. 0.625: Off by an order of magnitude; likely ignores decimal placement. Common Pitfalls: Treating 0.356 × 0.365 as a square (it is not). Rounding mid-steps instead of at the end, which can shift the hundredths place. Final Answer: 0.0638

Question 5

Recognize a perfect-square structure: Evaluate (3.65^2 + 2.35^2 − 2 × 2.35 × 3.65) / 1.69 by converting the numerator into a binomial square.

Accepted Answer

Introduction / Context: This is a direct application of the identity x^2 + y^2 − 2xy = (x − y)^2. Spotting this pattern allows you to reduce the problem to a simple square and then divide by a given constant. It is a staple technique in simplifying quadratic-looking expressions quickly. Given Data / Assumptions: Numerator: 3.65^2 + 2.35^2 − 2 × 3.65 × 2.35. Denominator: 1.69. Concept / Approach: Apply (x − y)^2 when you see x^2 + y^2 − 2xy. Here x = 3.65 and y = 2.35, so x − y = 1.30. Hence the numerator is simply 1.30^2. Then divide by 1.69 to finish. The numbers are intentionally chosen so that the final ratio is exact. Step-by-Step Solution: Compute x − y: 3.65 − 2.35 = 1.30.Therefore numerator = (1.30)^2 = 1.69.Quotient = 1.69 / 1.69 = 1. Verification / Alternative check: Note that 1.3^2 = 1.69 exactly, so the cancellation is perfect. Why Other Options Are Wrong: 1.69: That is the numerator before division, not the final value. 2.35 and 3.65: Misread constants or skipped squaring/identity step. Common Pitfalls: Changing the sign in −2xy and producing (x + y)^2 instead. Rounding 1.3^2 incorrectly; it is exactly 1.69. Final Answer: 1

Question 6

Compute a decimal expression with exponents and a linear denominator: Evaluate (0.5^3 × 0.6^3) / (0.5 × 0.5 − 0.3 + 0.6 × 0.6) accurately, simplifying powers first.

Accepted Answer

Introduction / Context: This item blends small decimal powers with a simple quadratic-like denominator. Calculating the powers first, then simplifying the denominator, and finally performing the division keeps errors in check. It is a good test of decimal place-value discipline and exponent handling. Given Data / Assumptions: Numerator: 0.5^3 × 0.6^3. Denominator: 0.5 × 0.5 − 0.3 + 0.6 × 0.6. No rounding is needed until the final step. Concept / Approach: Compute 0.5^3 and 0.6^3 exactly, multiply for the numerator, then evaluate each term in the denominator and combine. The final division can be expressed as a fraction to keep track of place values, then converted to a decimal with appropriate precision. Step-by-Step Solution: 0.5^3 = 0.125; 0.6^3 = 0.216.Numerator = 0.125 × 0.216 = 0.027.Denominator = (0.5 × 0.5) − 0.3 + (0.6 × 0.6) = 0.25 − 0.3 + 0.36 = 0.31.Quotient = 0.027 / 0.31 ≈ 0.08709677…Rounded to four significant figures (or to four decimal places), this is ≈ 0.0871. Verification / Alternative check: As a fraction, 0.027/0.31 = 27/3100 ≈ 0.008709677? Note the misplaced zero; correct decimal is 0.08709677… (31 × 0.0871 ≈ 2.7001). Why Other Options Are Wrong: 0.3 and 0.61: Far too large relative to the small numerator 0.027. 0.1: Close but still an overestimate; reflects rounding 0.027/0.27 by mistake. Common Pitfalls: Dropping a zero in the decimal when dividing by 0.31. Miscomputing 0.6^3 (some mistakenly take 0.6^2 = 0.36 and stop). Final Answer: 0.0871

Question 7

Compute the value of the decimal expression by applying order of operations: (.125 + .027) ÷ (.5 × .5 − 0.15 + .09) = ?   (Note: using the Recovery-First Policy, the middle term is interpreted as 0.15, a common transcription of 1.5 → 0.15.)

Accepted Answer

Introduction / Context: This problem reinforces careful handling of decimals and the order of operations (multiplication before addition/subtraction, then division). The expression appears to have a likely transcription slip: “1.5” in the denominator would make the final result negative and inconsistent with all positive choices. Under the Recovery-First Policy, we repair it minimally to 0.15, a common decimal adjacent to the digits shown, yielding a coherent result aligned with the options. Given Data / Assumptions: Expression to evaluate: (.125 + .027) ÷ (.5 × .5 − 0.15 + .09) Assume the middle term is 0.15 (not 1.5) so the problem has a consistent positive answer. All arithmetic is exact decimals with standard precedence. Concept / Approach: First simplify the numerator by direct addition. Then simplify the denominator by carrying out multiplication, followed by subtraction and addition. Finally divide the simplified numerator by the simplified denominator. Step-by-Step Solution: Numerator: .125 + .027 = 0.152.Denominator: .5 × .5 = 0.25.Then 0.25 − 0.15 + 0.09 = 0.10 + 0.09 = 0.19.Therefore value = 0.152 ÷ 0.19 = 0.8. Verification / Alternative check: Check by reversing: 0.8 × 0.19 = 0.152, which matches the numerator exactly. Hence the computed result is consistent. Why Other Options Are Wrong: 0.2 and 0.08: Result from incorrect division by 0.76 or 1.9, typically due to misplaced decimals. 1 and 0.5: Would require the denominator to be 0.152 or 0.304, not produced by the given terms. Common Pitfalls: Mistaking .5 × .5 as .25 is fine, but many then subtract 1.5 (if uncorrected), giving a negative denominator. Another frequent error is misplacing decimal digits when dividing 0.152 by 0.19. Final Answer: 0.8

Question 8

Evaluate using the cube identity: (0.47^3 − 0.33^3) / (0.47^2 + 0.47×0.33 + 0.33^2). Compute the exact decimal result.

Accepted Answer

Introduction / Context: This problem is a classic application of polynomial identities with decimals. Recognizing the form (a^3 − b^3) / (a^2 + ab + b^2) immediately simplifies computation and avoids long decimal multiplications. Given Data / Assumptions: a = 0.47, b = 0.33 Expression: (a^3 − b^3) / (a^2 + ab + b^2) Concept / Approach: Use the identity a^3 − b^3 = (a − b)(a^2 + ab + b^2). Dividing by (a^2 + ab + b^2) cancels that factor, leaving simply a − b. This identity works for any real numbers a, b, including decimals. Step-by-Step Solution: Start with (a^3 − b^3) / (a^2 + ab + b^2).Apply the factorization: a^3 − b^3 = (a − b)(a^2 + ab + b^2).Cancel the common factor (a^2 + ab + b^2): result = a − b.Compute a − b = 0.47 − 0.33 = 0.14. Verification / Alternative check: Approximate multiplication confirms the same outcome but is longer. The identity ensures exactness with far less effort. Why Other Options Are Wrong: 0.8 and 1: These do not match a − b for the given decimals. 15.51: Numerical distraction; it is roughly (0.39)^2/0.0099 style conflation, not the correct identity outcome. 0.047: Mistakes a − b with a or misreads decimal places. Common Pitfalls: Multiplying out cubes and squares directly and committing rounding errors; forgetting the exact identity that dramatically reduces work. Final Answer: 0.14

Question 9

Simplify a ratio of polynomial-like decimal forms: (1.04^2 + 1.04×0.04 + 0.04^2) / (1.04^3 − 0.04^3). Use sum of squares over difference of cubes.

Accepted Answer

Introduction / Context: The expression mirrors well-known polynomial identities but with decimal numbers. Leveraging those identities lets you avoid tedious multiplication and get an exact result instantly. Given Data / Assumptions: a = 1.04, b = 0.04 Numerator: a^2 + ab + b^2 Denominator: a^3 − b^3 Concept / Approach: Recall that a^3 − b^3 = (a − b)(a^2 + ab + b^2). Because the denominator contains (a^2 + ab + b^2) as a factor, the entire fraction simplifies to 1/(a − b). Step-by-Step Solution: Start: (a^2 + ab + b^2) / (a^3 − b^3).Factor the denominator: a^3 − b^3 = (a − b)(a^2 + ab + b^2).Cancel common factor (a^2 + ab + b^2).Result = 1 / (a − b) = 1 / (1.04 − 0.04) = 1 / 1.00 = 1. Verification / Alternative check: Direct numeric evaluation also yields 1 but is unnecessarily long. Identity-based simplification is exact and efficient. Why Other Options Are Wrong: 0.10, 0.1, 0.01: These imply treating (a − b) as 10, 10, or 100, which is incorrect. 1.04: Would require the denominator to be smaller than the numerator by factor 1/1.04, not the case here. Common Pitfalls: Attempting to compute a^3 and b^3 directly with decimals, which invites rounding mistakes; overlooking the factorization. Final Answer: 1

Question 10

Apply the sum-of-cubes identity with decimals: [(0.87)^3 + (0.13)^3] / [(0.87)^2 − 0.87×0.13 + (0.13)^2] = ?

Accepted Answer

Introduction / Context: Recognizing algebraic identities is the fastest route to accurate results. This problem encodes the sum-of-cubes identity in decimal form and asks for a clean simplification without heavy computation. Given Data / Assumptions: a = 0.87, b = 0.13 Numerator: a^3 + b^3 Denominator: a^2 − ab + b^2 Concept / Approach: The identity a^3 + b^3 = (a + b)(a^2 − ab + b^2) applies. Dividing by (a^2 − ab + b^2) cancels that factor, leaving simply a + b. With the given decimals, the answer is exact and elegant: 1.00. Step-by-Step Solution: Use a^3 + b^3 = (a + b)(a^2 − ab + b^2).Therefore [(a^3 + b^3)] / [(a^2 − ab + b^2)] = a + b.Compute a + b = 0.87 + 0.13 = 1.00. Verification / Alternative check: Directly raising decimals to powers also works but is slower and prone to rounding; the identity is exact and error-proof. Why Other Options Are Wrong: 0.87, 0.13, 0.74: These are component values or differences, not the sum demanded by the identity. 0.5: Arbitrary midpoint; unrelated to the identity here. Common Pitfalls: Confusing the identity with (a − b)^3 or attempting brute-force decimal exponentiation. Final Answer: 1

Question 11

Evaluate a nested decimal expression accurately: 3 / [ 3 + {(0.3 − 3.03) / (3 × 0.91)} ] = ?

Accepted Answer

Introduction / Context: This question checks precision with signed decimals and order of operations inside a complex denominator. Spotting simple cancellation makes the computation almost trivial once the inner fraction is recognized. Given Data / Assumptions: Expression: 3 / [ 3 + {(0.3 − 3.03) / (3 × 0.91)} ] All decimal arithmetic is exact; keep the sign when subtracting. Concept / Approach: Simplify the inner fraction first by computing its numerator and denominator. If they share magnitude (up to sign), the fraction becomes −1. Then evaluate the outer denominator and finally perform the division. Step-by-Step Solution: Inner numerator: 0.3 − 3.03 = −2.73.Inner denominator: 3 × 0.91 = 2.73.Thus inner fraction = −2.73 / 2.73 = −1.Overall denominator: 3 + (−1) = 2.Final value: 3 / 2 = 1.5. Verification / Alternative check: Convert to fractions out of 100 (e.g., 0.91 = 91/100) and observe exact cancellation to confirm the −1 step rigorously. Why Other Options Are Wrong: 15: As if multiplying instead of dividing by 2. 0.75: Inverts the final fraction 3/2 improperly. 1.75 and 1.25: Arise from arithmetic slips in the denominator (e.g., adding signs incorrectly). Common Pitfalls: Losing the negative sign from 0.3 − 3.03; miscomputing 3 × 0.91 as 2.79; or forgetting to simplify the inner term before the outer operations. Final Answer: 1.5

Question 12

Simplify a decimal–fraction mix carefully: { (0.1)^2 − (0.01)^2 } ÷ 0.0001 + 1 = ?   (Repair applied: division by 0.0001 then add 1, consistent with typical formatting and answer set.)

Accepted Answer

Introduction / Context: Mixed decimal and fractional forms often hide very simple structures. Here, a small difference of squares is scaled by dividing through 0.0001 (one ten-thousandth), then adjusted by adding 1. Interpreting the layout correctly is crucial; this repaired reading aligns with common textbook formatting and the provided choices. Given Data / Assumptions: Expression interpreted as: { (0.1)^2 − (0.01)^2 } ÷ 0.0001 + 1 All operations are exact; compute powers before subtraction and division. Concept / Approach: Compute (0.1)^2 and (0.01)^2 first, subtract, then divide by 0.0001. Finally add 1. Dividing by 0.0001 multiplies by 10,000, which greatly magnifies small differences. Step-by-Step Solution: (0.1)^2 = 0.01; (0.01)^2 = 0.0001.Difference: 0.01 − 0.0001 = 0.0099.Divide by 0.0001: 0.0099 ÷ 0.0001 = 0.0099 × 10,000 = 99.Add 1: 99 + 1 = 100. Verification / Alternative check: As fractions: 0.1 = 1/10 ⇒ (1/10)^2 = 1/100; 0.01 = 1/100 ⇒ (1/100)^2 = 1/10,000. Difference = 1/100 − 1/10,000 = 99/10,000. Dividing by 1/10,000 gives 99; plus 1 yields 100. Why Other Options Are Wrong: 101, 1010, 1101: Each assumes different placements of division or addition; they do not match the carefully evaluated sequence. 99: Omits the final +1 required by the expression. Common Pitfalls: Parsing the layout incorrectly (e.g., dividing by 1.0001 or adding inside the denominator), or forgetting that ÷ 0.0001 = × 10,000. Final Answer: 100

Question 13

Find the LCM of decimal numbers by scaling to integers: LCM of 3.0, 0.09, and 2.7. Show the scaling and factorization steps.

Accepted Answer

Introduction / Context: Least Common Multiple (LCM) for decimals is easiest to compute by converting all numbers to integers with a common power-of-ten multiplier, finding the LCM of those integers, then scaling back. This ensures exactness without floating-point errors. Given Data / Assumptions: Numbers: 3.0, 0.09, 2.7 Use a common scaling factor of 100 to clear two decimal places uniformly. Concept / Approach: Multiply each value by 100: 3.0 → 300; 0.09 → 9; 2.7 → 270. Find LCM(300, 9, 270) as integers. Then divide the result by 100 to restore the decimal scale. Step-by-Step Solution: Factorize: 300 = 2^2 * 3 * 5^2; 9 = 3^2; 270 = 2 * 3^3 * 5.LCM uses highest powers: 2^2, 3^3, 5^2.Compute LCM: 4 * 27 * 25 = 2700.Scale back by 100: 2700 ÷ 100 = 27. Verification / Alternative check: 27 ÷ 3.0 = 9 (integer), 27 ÷ 0.09 = 300 (integer), 27 ÷ 2.7 = 10 (integer). Hence 27 is a common multiple and is least by construction. Why Other Options Are Wrong: 2.7, 0.27, 0.027, 0.9: These are fractions of 27 and fail to be multiples of 0.09 simultaneously or to satisfy all three divisibility checks. Common Pitfalls: Using different scaling factors for each number or forgetting to scale back after computing the integer LCM. Final Answer: 27

Question 14

Compute the GCD (HCF) of decimal numbers by clearing decimals: GCD of 1.08, 0.36, and 0.90. Demonstrate exact integer reduction.

Accepted Answer

Introduction / Context: To find the greatest common divisor (GCD) of decimals exactly, convert them to integers by multiplying with a common power of ten, compute the GCD of the integers, and then scale back. This avoids rounding and ensures correctness. Given Data / Assumptions: Decimals: 1.08, 0.36, 0.90 Use a common factor of 100 to clear two decimal places. Concept / Approach: Multiply by 100: 1.08 → 108, 0.36 → 36, 0.90 → 90. Compute GCD(108, 36, 90). Then divide the GCD by 100 to return to decimal scale. Step-by-Step Solution: GCD(108, 36) = 36.GCD(36, 90) = 18.So the scaled GCD is 18. Scale back: 18 ÷ 100 = 0.18. Verification / Alternative check: Confirm divisibility: 1.08 ÷ 0.18 = 6; 0.36 ÷ 0.18 = 2; 0.90 ÷ 0.18 = 5. All are integers, confirming 0.18 divides each exactly. Why Other Options Are Wrong: 0.108, 0.06, 0.03: Each divides some but not all of the numbers evenly. 0.9: Larger than some inputs; not a common divisor of 0.36. Common Pitfalls: Scaling only some numbers or scaling back incorrectly; using approximate decimal GCDs without exact reduction. Final Answer: 0.18

Question 15

Convert the recurring decimal 0.1\u0305\u030536 (with 36 repeating after the initial 1) to a fraction in lowest terms. Identify the exact rational form.

Accepted Answer

Introduction / Context: Recurring decimals that include a non-repeating part followed by a repeating block can be converted to fractions using a standard algebraic technique. Here, the decimal is 0.1363636… where “36” repeats after an initial non-repeating “1”. Given Data / Assumptions: Let x = 0.1363636… with non-repeating part length m = 1 (the digit “1”) and repeating block length n = 2 (“36”). Concept / Approach: Use the formula derived from shifting decimals: If x = N.R. + R (repeating), then 10^(m+n) x − 10^m x eliminates the repeating tail. The fraction is then an integer over 9…90…0 with n nines and m zeros. Step-by-Step Solution: Let x = 0.1363636…100x = 13.636363… (shift by two for “36”).10x = 1.363636… (shift by one for the non-repeating “1”).Subtract: 100x − 10x = 13.636363… − 1.363636… = 12.273 = 12.273?? (better use integer blocks).Cleaner approach: write digits: up to first repeat: 0.1 | 36 36 36… ⇒ numerical block method gives (136 − 1) / (99 × 10) = 135 / 990.Reduce: 135/990 = 27/198 = 3/22. Verification / Alternative check: 3/22 ≈ 0.13636… Exactly matches the repeating pattern with “36”. Why Other Options Are Wrong: 136/999 and 136/990 mis-handle the lengths of the non-repeating and repeating parts. 136/1000 corresponds to the terminating decimal 0.136, not repeating. 13/90 is a simplified-looking fraction but does not reproduce 0.13636… Common Pitfalls: Forgetting to include a zero after the n nines to account for the m non-repeating digits or failing to reduce the final fraction completely. Final Answer: 3/22

Question 16

Add the decimals and give the exact result: 0.63 + 0.37 = ?   (Using Recovery-First Policy, these are ordinary terminating decimals, not repeating.)

Accepted Answer

Introduction / Context: This question assesses accurate addition of terminating decimals. The original prompt formatting could be misread as repeating decimals (overlines), but under the Recovery-First Policy we interpret them as ordinary terminating decimals 0.63 and 0.37, which produce a clean integer sum common in decimal-fraction practice sets. Given Data / Assumptions: Add 0.63 and 0.37 as standard terminating decimals. Align decimal places and add hundredths to hundredths, tenths to tenths. Concept / Approach: Writing the numbers with the same number of decimal places (two) and adding columnwise ensures that place values are handled correctly. Carrying from hundredths to tenths is straightforward. Step-by-Step Solution: 0.63 + 0.37 = (0.60 + 0.03) + (0.30 + 0.07).Group tenths and hundredths: (0.60 + 0.30) + (0.03 + 0.07) = 0.90 + 0.10.Sum: 1.00. Verification / Alternative check: As fractions: 0.63 = 63/100; 0.37 = 37/100; sum = 100/100 = 1. Why Other Options Are Wrong: 1.01 and 1.10: Result from carrying errors or misaligned decimal places. 0.99: Comes from subtracting 0.37 from 0.63 or omitting carry. 0.9: Ignores the hundredths sum reaching 0.10. Common Pitfalls: Misreading the problem as recurring decimals (which would yield 1.010101…); failing to align decimals; dropping the carry from 0.03 + 0.07. Final Answer: 1

Question 17

Compute the decimal sum accurately: Evaluate (0.3467 + 0.1333) and give the result to four decimal places.

Accepted Answer

Introduction / Context: This item checks comfort with addition of decimals and correct placement of the decimal point. The original formatting had spaces within decimals; we normalize it as 0.3467 + 0.1333 and add them carefully. Given Data / Assumptions: Addends: 0.3467 and 0.1333. Standard base-10 place-value arithmetic applies. Report the exact decimal sum (no rounding needed beyond the natural precision). Concept / Approach: Align decimals by place value: ten-thousandths with ten-thousandths, etc. Add column-wise from right to left, carrying over if a column sums to 10 or more tenths of that place. Step-by-Step Solution: Write vertically and align places:0.3467+0.1333= 0.4800 Verification / Alternative check: Break each number by place values: (0.3000 + 0.1000) + (0.0400 + 0.0300) + (0.0060 + 0.0030) + (0.0007 + 0.0003) = 0.4000 + 0.0700 + 0.0090 + 0.0010 = 0.4800. Why Other Options Are Wrong: 0.48 omits trailing precision, while the exact four-place result is 0.4800. 0.4801 and 0.481 arise from a mistaken carry. 0.47 is a subtraction-like error or truncation. Common Pitfalls: Misaligning digits (e.g., adding hundredths to thousandths), or prematurely rounding before completing the addition which can shift the last digit. Final Answer: 0.4800

Question 18

Apply decimal subtraction using place value: Evaluate (3.57 − 2.14).

Accepted Answer

Introduction / Context: The question assesses straightforward decimal subtraction, reinforcing place-value alignment and borrow logic for tenths and hundredths. Given Data / Assumptions: Compute 3.57 − 2.14. Decimals are in hundredths; align digits before subtracting. Concept / Approach: Write the numbers one under the other with decimal points aligned. Subtract hundredths, then tenths, then the units digit, borrowing from the next left place if necessary. Step-by-Step Solution: Hundredths: 7 − 4 = 3Tenths: 5 − 1 = 4Ones: 3 − 2 = 1Therefore, 3.57 − 2.14 = 1.43 Verification / Alternative check: Think in parts: (3 + 0.57) − (2 + 0.14) = (3 − 2) + (0.57 − 0.14) = 1 + 0.43 = 1.43. Why Other Options Are Wrong: 1.4301 and 1.403 introduce spurious digits. 1.42 and 1.44 are off by a hundredth due to a carry/borrow mistake. Common Pitfalls: Failing to align decimals, subtracting 14 from 57 incorrectly, or adding instead of subtracting the hundredths place. Final Answer: 1.43

Question 19

Add three decimal numbers carefully: Evaluate (2.47 + 3.53 + 0.05) and choose the exact sum.

Accepted Answer

Introduction / Context: Accurate addition of decimals requires alignment of place values and careful handling of carries. This skill underpins percentage, money, and measurement problems. Given Data / Assumptions: Addends: 2.47, 3.53, and 0.05. We seek the exact sum, not an approximation. Concept / Approach: Align decimals and add column by column: hundredths, tenths, ones. Combine 2.47 and 3.53 first (a neat whole), then include 0.05. Step-by-Step Solution: 2.47 + 3.53 = 6.00 (since 0.47 + 0.53 = 1.00)Now add 0.05: 6.00 + 0.05 = 6.05 Verification / Alternative check: Add directly by places: (2 + 3 + 0) + (0.4 + 0.5 + 0.0) + (0.07 + 0.03 + 0.05) = 5 + 0.9 + 0.15 = 6.05. Why Other Options Are Wrong: 6.06 occurs if you mistakenly add 0.06 instead of 0.05. 6.01 results from mis-adding hundredths. 6.00 and 5.95 ignore or mis-handle the 0.05 term. Common Pitfalls: Not noticing that 2.47 + 3.53 makes an exact whole (which simplifies the computation), or misplacing the final hundredths digit. Final Answer: 6.05

Question 20

Convert a recurring decimal to a fraction: Express the repeating decimal 4.12 (where 12 repeats) as a single simplified fraction.

Accepted Answer

Introduction / Context: Recurring decimals such as 4.121212... can be converted exactly to rational numbers. Mastering this technique helps move between decimal and fractional forms without rounding. Given Data / Assumptions: Repeating decimal: 4.12 with the block 12 repeating indefinitely (4.121212...). Find an exact fraction in simplest terms. Concept / Approach: Let x = 4.121212.... For a two-digit repeat, multiply by 100 to shift the decimal so that subtraction eliminates the repeating part. Step-by-Step Solution: Let x = 4.121212...100x = 412.121212...Subtract: 100x − x = 412.121212... − 4.121212... = 408So 99x = 408 ⇒ x = 408/99Reduce 408/99 by dividing numerator and denominator by 3: 136/33 Verification / Alternative check: Write the integer part plus the repeating fractional part: 4 + 0.121212...; and 0.121212... = 12/99 = 4/33. Then 4 + 4/33 = (132 + 4)/33 = 136/33, confirming the result. Why Other Options Are Wrong: 411/99 corresponds to 4.1515..., not 4.1212.... 52/9 equals approximately 5.777..., too large. 411/90 ≈ 4.566..., also incorrect. Common Pitfalls: Using 10x instead of 100x for a two-digit repeat, or failing to simplify the resulting fraction completely. Final Answer: 136/33

Decimal Fraction Questions