Question 1

Find the incorrect term in the following number series. Series: 380, 188, 92, 48, 20, 8, 2

Accepted Answer

Introduction / Context: Many decreasing series repeatedly apply the same operation. Here the intended operation is “halve and subtract 2.” Detecting this single-step rule exposes the term that does not follow it. Given Data / Assumptions: Series: 380, 188, 92, 48, 20, 8, 2 Hypothesis: next = (current / 2) − 2. Concept / Approach: Verify each transition using the formula next = (current / 2) − 2. Any transition that fails indicates the wrong term at the arrival point. Step-by-Step Solution: From 380: (380 / 2) − 2 = 190 − 2 = 188 ✓ From 188: (188 / 2) − 2 = 94 − 2 = 92 ✓ From 92: (92 / 2) − 2 = 46 − 2 = 44 (but the series shows 48 ✗) Continuing the rule from 44: (44 / 2) − 2 = 22 − 2 = 20 ✓; (20 / 2) − 2 = 10 − 2 = 8 ✓; (8 / 2) − 2 = 4 − 2 = 2 ✓. Verification / Alternative check: Replacing 48 with 44 produces a fully consistent chain using a single, simple operation. Why Other Options Are Wrong: 188, 20, 8 align perfectly with the rule; they should not be removed. Common Pitfalls: Trying alternating add/subtract adjustments instead of noticing the cleaner “halve and subtract 2.” Final Answer: 48

Question 2

Find the incorrect term in the following number series. Series: 16, 22, 30, 45, 52, 66

Accepted Answer

Introduction / Context: This checks whether you can detect steadily increasing step sizes. When step sizes should rise by a fixed amount, any term that disrupts that growth is incorrect. Given Data / Assumptions: Series: 16, 22, 30, 45, 52, 66 Intended steps likely increase by 2 each time. Concept / Approach: Compute differences and see if they form an arithmetic progression. If so, regenerate the expected term and compare. Step-by-Step Solution: Target step pattern: +6, +8, +10, +12, +14. Compute with this pattern: 16 + 6 = 22; 22 + 8 = 30; 30 + 10 = 40 (but the series shows 45 ✗); 40 + 12 = 52; 52 + 14 = 66. Hence, the fourth term should be 40, not 45. Verification / Alternative check: Substituting 40 for 45 yields consistent differences of 6, 8, 10, 12, 14. Why Other Options Are Wrong: 30, 52, 66 all align with the intended difference progression and therefore are not wrong. Common Pitfalls: Accepting irregular jumps as random rather than testing for an orderly increase in step size. Final Answer: 45

Question 3

Find the incorrect term in the following number series. Series: 10, 26, 74, 218, 654, 1946, 5834

Accepted Answer

Introduction / Context: Some sequences apply the same transformation each time. Here the intended rule is multiply by 3 and then subtract 4. Identifying the consistent rule reveals the single term that does not comply. Given Data / Assumptions: Series: 10, 26, 74, 218, 654, 1946, 5834 Hypothesis: next = (current * 3) − 4. Concept / Approach: Test the rule across each transition. The term produced by a failed transition identifies the anomaly. Step-by-Step Solution: 10 * 3 − 4 = 30 − 4 = 26 ✓ 26 * 3 − 4 = 78 − 4 = 74 ✓ 74 * 3 − 4 = 222 − 4 = 218 ✓ 218 * 3 − 4 = 654 − 4 = 650 (but the series shows 654 ✗) Continuing correctly: 650 * 3 − 4 = 1950 − 4 = 1946 ✓; 1946 * 3 − 4 = 5838 − 4 = 5834 ✓. Verification / Alternative check: Replacing 654 with 650 makes the rule hold for all steps. Why Other Options Are Wrong: 26, 74, 218 each exactly equals 3×previous − 4; they are consistent and thus correct. Common Pitfalls: Missing the constant subtraction after the multiplication. Final Answer: 654

Question 4

Find the incorrect term in the following number series. Series: 24576, 6144, 1536, 386, 96, 24

Accepted Answer

Introduction / Context: This decreasing series should follow repeated division by 4. A single number not equal to the previous term divided by 4 is the misfit. Given Data / Assumptions: Series: 24576, 6144, 1536, 386, 96, 24 Expected rule: next = current / 4. Concept / Approach: Verify each transition with division by 4. The term reached by a failed division is the incorrect one. Step-by-Step Solution: 24576 / 4 = 6144 ✓ 6144 / 4 = 1536 ✓ 1536 / 4 = 384 (but the series shows 386 ✗) Continuing correctly: 384 / 4 = 96 ✓; 96 / 4 = 24 ✓. Verification / Alternative check: Replacing 386 with 384 makes the entire chain a perfect /4 ladder. Why Other Options Are Wrong: 96, 1536, 6144 all are exact quarters of their predecessors or produce correct successors by /4. Common Pitfalls: Looking for alternating operations when a single consistent division explains all transitions. Final Answer: 386

Question 5

Number Series — Find the Wrong Term Identify the single incorrect term in the sequence: 10, 14, 28, 32, 64, 68, 132.

Accepted Answer

Introduction / Context: This problem asks you to spot the incorrect number in a deterministic numeric pattern. Such questions commonly alternate operations like addition and multiplication. Recognizing the repeating cycle is the key to finding the wrong term quickly in aptitude tests. Given Data / Assumptions: Sequence provided: 10, 14, 28, 32, 64, 68, 132 Assume exactly one term is inconsistent with an otherwise regular rule. Operations may alternate (for example, +k then *m). Concept / Approach: Check if the series alternates between adding a fixed number and then doubling. This is a frequent pattern: +c, *2, +c, *2, and so on. Validate each transition and see which value breaks the cycle. Step-by-Step Solution: 10 → 14: +414 → 28: *228 → 32: +432 → 64: *264 → 68: +468 → next should be *2 = 136But the given next is 132, which violates the *2 step. Verification / Alternative check: Recompute each step: every pair fits “+4 then *2” until the final transition. The correct last term should be 136, so the provided 132 is wrong. Why Other Options Are Wrong: 28, 32, 64: Each fits perfectly into the alternating “+4, *2” pattern and is therefore not the erroneous term. Common Pitfalls: Assuming a single arithmetic or geometric progression without testing for alternating operations. Always examine differences and ratios in tandem to reveal two-step cycles. Final Answer: 132

Question 6

Number Series — Find the Wrong Term Spot the incorrect term in the sequence: 46080, 3840, 384, 48, 24, 2, 1.

Accepted Answer

Introduction / Context: Wrong-number series questions often hide a clean mathematical rule that one entry fails to follow. Here, the values shrink by division with systematically chosen even numbers. Your task is to identify the lone outlier. Given Data / Assumptions: Series: 46080, 3840, 384, 48, 24, 2, 1 We expect a consistent rule (e.g., divide by descending even numbers). Exactly one term is wrong. Concept / Approach: Test a natural descending-division rule by even numbers: divide by 12, then by 10, then by 8, then by 6, then by 4, then by 2. This kind of neat halving of the divisor by 2 each step (12→10→8→6→4→2) is typical in such puzzles. Step-by-Step Solution: 46080 / 12 = 3840 ✔3840 / 10 = 384 ✔384 / 8 = 48 ✔48 / 6 = 8 (but the sequence shows 24 ✖)Continuing the correct pattern: 8 / 4 = 2 ✔2 / 2 = 1 ✔Therefore, the only mismatch is the term 24; it should have been 8 to maintain the rule. Verification / Alternative check: Replacing 24 with 8 yields the consistent sequence: 46080, 3840, 384, 48, 8, 2, 1, which strictly follows /12, /10, /8, /6, /4, /2. Why Other Options Are Wrong: 384, 48, 2: Each fits the division-by-decreasing-even-numbers pattern and is therefore correct. Common Pitfalls: Accepting an arbitrary mix of divisors. In exam settings, expect a clean descending or ascending structure; once identified, any inconsistent term becomes obvious. Final Answer: 24

Question 7

Number Series — Find the Wrong Term (Alternating Subsequence Insight) Identify the incorrect number in: 89, 78, 86, 80, 85, 82, 83.

Accepted Answer

Introduction / Context: Some wrong-number series are best solved by splitting into two interleaved subsequences (odd and even positions). When each subsequence follows its own steady rule, the lone mismatch becomes visible. Given Data / Assumptions: Full sequence: 89, 78, 86, 80, 85, 82, 83 Positions: 1-based indexing helps identify alternating patterns. Exactly one term is wrong. Concept / Approach: Separate the sequence by position parity. Odd positions (1, 3, 5, 7): 89, 86, 85, 83Even positions (2, 4, 6): 78, 80, 82The even-position subsequence clearly increases by +2 each time (78 → 80 → 82). The odd-position subsequence should ideally form a simple steady decrease, typically by 2 steps to mirror even regularity (89 → 87 → 85 → 83). Step-by-Step Solution: Expected odd subsequence: 89, 87, 85, 83Given odd subsequence: 89, 86, 85, 83Mismatch at position 3 (overall sequence index): 86 should have been 87. Verification / Alternative check: If 86 is replaced by 87, both subsequences become perfectly regular: odd positions decrease by 2 each step and even positions increase by 2 each step. Why Other Options Are Wrong: 78, 82, 83: These fit the +2 even subsequence or the −2 odd subsequence properly and therefore are not erroneous. Common Pitfalls: Examining only consecutive differences across the whole list can obscure a clean interleaving structure. Always test odd/even positions when patterns seem jagged. Final Answer: 86

Question 8

Number Series — Find the Wrong Term (Interleaved Odd/Even Positions) Which number is incorrect in the sequence: 0, 2, 3, 5, 8, 10, 15, 18, 24, 26, 35?

Accepted Answer

Introduction / Context: Here the sequence is best understood by splitting into two interleaved subsequences. Many test-setters design one parity (odd or even positions) to follow a simple rule like adding consecutive odd numbers, revealing the outlier when the other parity is checked. Given Data / Assumptions: Main sequence: 0, 2, 3, 5, 8, 10, 15, 18, 24, 26, 35 Index positions (1-based): odd positions = 1,3,5,7,9,11; even positions = 2,4,6,8,10. Concept / Approach: Split the list: Odd positions: 0, 3, 8, 15, 24, 35 Even positions: 2, 5, 10, 18, 26 Step-by-Step Solution: Odd subsequence differences: 0→3 (+3), 3→8 (+5), 8→15 (+7), 15→24 (+9), 24→35 (+11). This is a perfect +3, +5, +7, +9, +11 pattern (consecutive odd numbers).Even subsequence should mirror a similar steadily growing pattern, but:2→5 (+3), 5→10 (+5), 10→18 (+8), 18→26 (+8)To remain consistent with consecutive odds, after +5 we expect +7, not +8. Therefore the value after 10 should be 17, not 18. Verification / Alternative check: Replacing 18 with 17 makes the even subsequence +3, +5, +7, +9 and the merged sequence becomes fully regular with both parities following “add consecutive odd numbers”. Why Other Options Are Wrong: 10, 24, 26: These align with the intended growth pattern once 18 is corrected, so they are not the erroneous term. Common Pitfalls: Looking only at overall differences can be misleading. Many crafted sequences hide elegance in positional interleaving. Always test odd/even strands. Final Answer: 18

Question 9

Number Series — Find the Wrong Term (Descending Differences as Multiples of 11) Identify the incorrect number: 325, 259, 202, 160, 127, 105, 94.

Accepted Answer

Introduction / Context: Many wrong-number questions rely on successive differences forming a clean pattern. Here, the cleanest structure is differences descending by 11 each step, a hallmark of exam puzzle design. Given Data / Assumptions: Sequence: 325, 259, 202, 160, 127, 105, 94 Exactly one number is wrong. Test first differences for a tidy progression (e.g., equal steps or steps reducing by a fixed amount). Concept / Approach: Compute consecutive differences and look for a simple descending pattern, especially multiples of a constant such as 11. Step-by-Step Solution: 325 → 259 = −66259 → 202 = −57 (suspect)202 → 160 = −42160 → 127 = −33127 → 105 = −22105 → 94 = −11All differences except −57 are multiples of 11: −66, −42, −33, −22, −11.If we replace 202 with 204, the differences become −66, −55, −44, −33, −22, −11, which is a perfect arithmetic ladder descending by 11 each time. Verification / Alternative check: Only the transition 259 → 202 breaks the “descending multiples of 11” rule. Adjusting that term to 204 aligns the entire sequence; therefore, 202 is the wrong entry. Why Other Options Are Wrong: 259, 127, 94: These participate correctly in the neat −66, −44, −22, −11 cadence (once the erroneous 202 is fixed) and are not incorrect. Common Pitfalls: Stopping after one irregular step without testing whether a single correction yields a perfectly consistent pattern across all differences. Final Answer: 202

Question 10

Number Series — Find the Wrong Term (Add 1110 Each Step) Which number is incorrect in: 1236, 2346, 3456, 4566, 5686?

Accepted Answer

Introduction / Context: Some sequences add a fixed constant each step. Spotting a neat addition such as +1110 quickly reveals the outlier that fails to follow the rule. Given Data / Assumptions: Numbers: 1236, 2346, 3456, 4566, 5686 Assume a single wrong term. Test for constant addition. Concept / Approach: Check whether each term equals the previous plus 1110. This pattern aligns with the visible digit structures and is easy to validate by subtraction. Step-by-Step Solution: 2346 − 1236 = 1110 ✔3456 − 2346 = 1110 ✔4566 − 3456 = 1110 ✔5686 − 4566 = 1120 ✖ (should be 1110)Hence, the last value should be 4566 + 1110 = 5676, not 5686. Verification / Alternative check: Replacing 5686 with 5676 yields a perfect constant increment sequence. Therefore 5686 is the incorrect term. Why Other Options Are Wrong: 1236, 3456, 4566: Each maintains the +1110 progression; they are consistent and correct. Common Pitfalls: Overcomplicating with multiplicative rules. Always try simple constant addition or subtraction first when digits suggest a steady shift. Final Answer: 5686

Question 11

Number Series — Find the Wrong Term (Add Cubes Pattern) Identify the incorrect number in: 93, 309, 434, 498, 521, 533.

Accepted Answer

Introduction / Context: Many crafted sequences add successive cubes to generate the next term. If one step deviates from the expected cube addition, that term is the wrong number in the series. Given Data / Assumptions: Sequence: 93, 309, 434, 498, 521, 533 Exactly one term is incorrect. Suspect additions of 6^3, 5^3, 4^3, 3^3, 2^3, ... Concept / Approach: Compute consecutive differences and compare them to consecutive cubes: 216, 125, 64, 27, 8, ... This reveals where the deviation occurs. Step-by-Step Solution: 309 − 93 = 216 = 6^3 ✔434 − 309 = 125 = 5^3 ✔498 − 434 = 64 = 4^3 ✔521 − 498 = 23 ✖ (should be 27 = 3^3)533 − 521 = 12 ✖ (should be 8 = 2^3) — this mismatch is a consequence of the earlier error.Correct fourth step: 498 + 27 = 525. Hence, 521 is the wrong term (it breaks the cube pattern first). Verification / Alternative check: Correct sequence would continue as 93, 309 (+216), 434 (+125), 498 (+64), 525 (+27), 533 (+8). This validates that 521 is the lone incorrect term. Why Other Options Are Wrong: 309, 434, 498: These conform exactly to adding 6^3, 5^3, and 4^3 respectively. Common Pitfalls: Stopping the check after a single difference. Always examine multiple consecutive steps to confirm a hypothesized pattern like cubes, squares, or factorial increments. Final Answer: 521

Question 12

Alphabet Series — Complete the Analogy WFB, TGD, QHG, ? → Choose the next three-letter term.

Accepted Answer

Introduction / Context: Alphabet series problems often apply independent patterns to each character position. Spotting arithmetic shifts on alphabet indices (A=1 to Z=26) unlocks the next term efficiently. Given Data / Assumptions: Given terms: WFB, TGD, QHG, ? We assume consistent letter-wise transformations. Concept / Approach: Analyze each letter position separately and track the index changes. Step-by-Step Solution: First letters: W(23) → T(20) → Q(17): −3 each step → next = 17 − 3 = 14 → NSecond letters: F(6) → G(7) → H(8): +1 each step → next = 8 + 1 = 9 → IThird letters: B(2) → D(4) → G(7): +2, +3 → next increment +4 → 7 + 4 = 11 → KTherefore, the next term is NIK. Verification / Alternative check: The progression by −3 (first), +1 (second), and +2,+3,+4 (third) is internally consistent and yields a unique result. Why Other Options Are Wrong: NIJ, NJK, OIK, PJK: Each deviates from at least one positional rule (e.g., third-letter increment of +4 or the first-letter −3 step). Common Pitfalls: Treating the triplet as a single object instead of analyzing positions independently. Always break it down to letter-wise arithmetic on indices. Final Answer: NIK

Question 13

Alphabet Pairs — Continue the Pattern AZ, GT, MN, ?, YB → Choose the correct missing pair.

Accepted Answer

Introduction / Context: Paired-letter sequences usually feature a rule for the first letters and another (often mirrored) rule for the second letters. This symmetric behavior is common in exam patterns. Given Data / Assumptions: Pairs: AZ, GT, MN, ?, YB Use A=1, B=2, ..., Z=26 indexing. Concept / Approach: Track first letters and second letters separately to reveal constant steps. Step-by-Step Solution: First letters: A(1) → G(7) → M(13) → ? → Y(25). Step size: +6 repeatedly → next first letter = 13 + 6 = 19 → S.Second letters: Z(26) → T(20) → N(14) → ? → B(2). Step size: −6 repeatedly → next second letter = 14 − 6 = 8 → H.Thus the missing pair is SH. Verification / Alternative check: Continuing +6 for the first letters and −6 for the second letters neatly produces the final given pair YB, confirming consistency. Why Other Options Are Wrong: JH, SK, TS: These break either the +6 first-letter or −6 second-letter rule. Common Pitfalls: Mixing up the order or applying the step to both letters in the same direction. Many puzzles intentionally mirror the steps to opposite directions for symmetry. Final Answer: SH

Question 14

Alphabet Series — Next Letter with Growing Steps Complete the sequence: H, I, K, N, ?

Accepted Answer

Introduction / Context: Alphabet series with single letters often advance by step sizes that increase by 1 each time. Detecting the incremental jump (+1, +2, +3, …) determines the next letter quickly. Given Data / Assumptions: Sequence: H, I, K, N, ? Indexing: A=1, ..., Z=26. Assume increasing step sizes. Concept / Approach: Compute the jumps between successive letters and extrapolate the next jump by adding 1 to the previous step size. Step-by-Step Solution: H(8) → I(9): +1I(9) → K(11): +2K(11) → N(14): +3Next step should be +4.N(14) + 4 = 18 → R. Verification / Alternative check: The pattern of step sizes (1, 2, 3, 4) is strictly increasing by 1, confirming R uniquely. Why Other Options Are Wrong: O (15), Q (17), S (19): These represent +1, +3, or +5 from N, not the required +4. Common Pitfalls: Assuming constant differences or skipping the check on step-size growth. Always list numeric indices to avoid miscounting letter gaps. Final Answer: R

Question 15

Alphabet series with two interleaved progressions: Z, S, W, O, T, K, Q, G, ?, ? Find the next two letters by analyzing the pattern at odd and even positions separately.

Accepted Answer

Introduction / Context: This verbal reasoning question tests recognition of interleaved alphabet sequences. Many letter-series puzzles are built from two simpler patterns woven together: one rule applies to letters in odd positions and another rule to letters in even positions. Spotting and extending both rules leads to the correct missing letters. Given Data / Assumptions: Series: Z, S, W, O, T, K, Q, G, ?, ? Alphabet positions: A=1, B=2, …, Z=26. Assume a consistent rule at odd indices and another at even indices. Concept / Approach: Separate the sequence into two lists: the letters in odd places and the letters in even places. Compute their position values and look for steady increments or decrements. Project each rule forward to obtain the 9th and 10th letters. Step-by-Step Solution: Odd positions (1,3,5,7,…): Z(26), W(23), T(20), Q(17), ?Rule at odd positions: subtract 3 each time (26→23→20→17→14).Next odd-position letter = 14 = N.Even positions (2,4,6,8,…): S(19), O(15), K(11), G(7), ?Rule at even positions: subtract 4 each time (19→15→11→7→3).Next even-position letter = 3 = C. Verification / Alternative check: Why Other Options Are Wrong: N, D or O, C or O, D violate at least one of the constant-step rules (they do not match −3 for odd or −4 for even indices). Common Pitfalls: Trying to force a single-step pattern across all terms, or overlooking that two independent streams are interleaved. Always test odd/even position rules when direct patterns look inconsistent. Final Answer: N, C

Question 16

Alphabet series: A, G, L, P, S, ? Determine the next letter by examining the jump sizes between alphabetical positions.

Accepted Answer

Introduction / Context: This is a classic letter-series problem built on arithmetic jumps in alphabet positions. The task is to find a consistent step between consecutive letters and then extend that rule to predict the next item. Given Data / Assumptions: Series: A, G, L, P, S, ? Alphabet index: A=1, …, Z=26. Assume a steady change (increase) in position values. Concept / Approach: Convert each letter to its numeric position, compute the successive differences, and look for a consistent pattern. Apply the same increment to the last known term to get the answer. Step-by-Step Solution: Positions: A(1), G(7), L(12), P(16), S(19).Differences: +6, +5, +4, +3 (a decreasing increment by 1 each time).Next difference should be +2.Next letter = S(19) + 2 = 21 → U. Verification / Alternative check: Why Other Options Are Wrong: W, X, Y require larger jumps (+4, +5, +6) that contradict the clearly shrinking step size. Common Pitfalls: Assuming a constant step size or skipping the numeric translation. Converting letters to numbers helps reveal simple arithmetic patterns instantly. Final Answer: U

Question 17

Three-letter blocks with modular +6 shifts (mod 26): ajs, gpy, ?, sbk, yhq Find the missing triplet by tracking each character’s independent progression.

Accepted Answer

Introduction / Context: This pattern-recognition problem uses blocks of three letters. Each position within the triplet (1st, 2nd, 3rd) follows its own arithmetic progression around the alphabet. We extend those position-wise rules using modular arithmetic (wrapping after Z→A). Given Data / Assumptions: Triplets: ajs, gpy, ?, sbk, yhq Alphabet indices: a=1, …, z=26. Progressions may wrap around at 26 (modulo 26 arithmetic). Concept / Approach: Split the sequence into three independent letter streams: all first letters, all second letters, and all third letters. Determine each stream’s rule (increment per step), then compute the missing letters. Step-by-Step Solution: First letters: a(1) → g(7) → ? → s(19) → y(25). The step is consistently +6 mod 26, so missing = m(13).Second letters: j(10) → p(16) → ? → b(2) → h(8). Again +6 mod 26: 10→16→22 (v)→28≡2 (b)→8 (h). Missing second letter = v.Third letters: s(19) → y(25) → ? → k(11) → q(17). With +6 mod 26: 19→25→31≡5 (e)→11 (k)→17 (q). Missing third letter = e.Therefore the missing triplet is m v e. Verification / Alternative check: Why Other Options Are Wrong: dmv, oua, qzi each break at least one of the +6 mod 26 streams (first, second, or third letter sequence). Common Pitfalls: Trying to relate letters across a triplet instead of tracking each column separately, or forgetting to wrap beyond Z using modulo arithmetic. Final Answer: mve

Question 18

Growing blocks of consecutive letters: AB, DEF, HIJK, ?, STUVWX Identify the missing block by continuing the length and starting-letter patterns.

Accepted Answer

Introduction / Context: This alphabet puzzle builds blocks of consecutive letters with increasing lengths. The starting letter advances through the alphabet as each block grows by one character compared to the previous block. Given Data / Assumptions: Blocks: AB (length 2), DEF (length 3), HIJK (length 4), ?, STUVWX (length 6) After AB ends at B, the next block begins at D; after DEF ends at F, the next begins at H, and so on. Concept / Approach: Observe two rules: (1) block length increases by +1 each time, and (2) each block is a run of consecutive letters starting just after the previous block’s end (with a fixed gap of one letter between block starts: A→D→H→L→S). Step-by-Step Solution: Known lengths: 2, 3, 4, ?, 6 → so the missing block must be length 5.Starting letters: A, D, H, ?, S. The pattern adds +3 to the start each time (A→D→H→L→S).Therefore, begin the missing block at L and take 5 consecutive letters: L, M, N, O, P.Missing block = LMNOP. Verification / Alternative check: Why Other Options Are Wrong: LMNO has only 4 letters; MNOPQ and QRSTU start at the wrong letters relative to the +3 start pattern. Common Pitfalls: Ignoring block length growth, or starting the missing block from the wrong letter. Always confirm both length and start-letter sequences. Final Answer: LMNOP

Question 19

Interleaved letter streams (−5 and +5): Y, B, T, G, O, ? Find the next letter by separating odd and even positions into distinct progressions.

Accepted Answer

Introduction / Context: Here the sequence alternates between two simple arithmetic rules on alphabet positions. By pulling apart odd and even terms, we can extend each subsequence independently and then recombine to get the next letter. Given Data / Assumptions: Series: Y, B, T, G, O, ? Alphabet index: A=1 to Z=26. Assume two interleaved progressions (odd vs even positions). Concept / Approach: Compute positions of letters in odd slots (1,3,5,…) and even slots (2,4,6,…). Identify a constant increment/decrement in each stream and extend the appropriate one for the next term (here, the 6th term). Step-by-Step Solution: Odd positions: 1=Y(25), 3=T(20), 5=O(15). Rule: −5 each time (25→20→15).Even positions: 2=B(2), 4=G(7), 6=? Rule: +5 each time (2→7→12).Next even-position letter = 12 → L. Verification / Alternative check: Why Other Options Are Wrong: N, M, K do not match the +5 even-position rule from B→G→L. Common Pitfalls: Mixing the two interleaved sequences, or trying to apply one rule to the entire list instead of splitting by parity of positions. Final Answer: L

Question 20

Alternating pair-pattern in letters: C, Z, F, X, I, V, L, T, O, ?, ? Determine the next two letters by tracking two simultaneous streams.

Accepted Answer

Introduction / Context: This series alternates between two logical progressions: one stream climbs forward through the alphabet by a fixed step, and the other stream moves backward by a fixed step. Recognizing and extending both simultaneously yields the two missing letters. Given Data / Assumptions: Full sequence: C, Z, F, X, I, V, L, T, O, ?, ? Alphabet index mapping A=1 … Z=26. Positions 1,3,5,… form Stream A; positions 2,4,6,… form Stream B. Concept / Approach: Separate odd- and even-position letters. Compute their numeric positions and identify a constant step for each stream. Continue Stream B for the 10th letter and Stream A for the 11th letter. Step-by-Step Solution: Stream A (odd positions): C(3), F(6), I(9), L(12), O(15). Rule: +3 each step. Next odd letter = 15 + 3 = 18 → R.Stream B (even positions): Z(26), X(24), V(22), T(20), ?. Rule: −2 each step. Next even letter = 20 − 2 = 18 → R.Therefore, 10th letter (even) = R, 11th letter (odd) = R. Verification / Alternative check: Why Other Options Are Wrong: O, P / P, Q / S, R each breaks at least one of the constant-step rules for Stream A or Stream B. Common Pitfalls: Attempting to find one rule for all positions instead of separating into odd/even streams with distinct step sizes. Final Answer: R, R

Series Completion Questions