More Questions from Decimal Fraction

The value of $$ \frac{241.6 \times 0.3814 \times 6.842}{0.4618 \times 38.25 \times 73.65} $$ is close to

Aptitude Decimal Fraction Difficulty: Hard
Choose an option
  • A
    0.2
  • B
    0.4
  • C
    0.6
  • D
    1

Answer

Correct Answer: 0.4

Explanation

### Strategy & Logic When options are tightly clustered (like $0.2, 0.4, 0.6, 1$), basic order-of-magnitude approximation isn't enough. We must use **Paired Approximation**—matching terms in the numerator to terms in the denominator to create clean, small ratios that we multiply together. ### Step-by-Step Solution **Given:** $$ \frac{241.6 \times 0.3814 \times 6.842}{0.4618 \times 38.25 \times 73.65} $$ **Deduction (Paired Ratios):** * Instead of multiplying across, form pairs of numbers (one from the top, one from the bottom) that are easy to divide. * **Pair 1:** $241.6$ and $38.25$ Approximate: $240 / 40 = 6$. (More precise check: $240 / 38 \approx 6.3$) * **Pair 2:** $0.3814$ and $0.4618$ Approximate: $0.38 / 0.46 = 38 / 46 \approx 19 / 23$. Since $19/23$ is roughly $5/6$, the ratio is about $0.83$. * **Pair 3:** $6.842$ and $73.65$ Approximate: $7 / 74 \approx 1 / 10 = 0.1$. (More precise check: $6.8 / 73.6 \approx 0.093$) * Now multiply these individual simplified ratios together: $$ 6.3 \times 0.83 \times 0.093 $$ * Multiply the first two: $6.3 \times 0.83 \approx 5.2$ * Multiply by the final ratio: $5.2 \times 0.093 \approx 0.48$ * We have an estimated result of $\sim 0.48$. * Look at the given options: $0.2, 0.4, 0.6, 1$. * Calculate the absolute distance: Distance to 0.4: $|0.48 - 0.40| = 0.08$ Distance to 0.6: $|0.60 - 0.48| = 0.12$ * Since $0.48$ is mathematically closer to $0.4$ than to $0.6$, the closest option is $0.4$. ### Exam Strategy & Shortcut **Rounding Compensation:** When approximating, if you round a numerator up, try to round the denominator up to maintain the true ratio. Let's do a faster mental block: $240 \times 0.4 \times 7 \approx 96 \times 7 \approx 672$ $0.5 \times 38 \times 74 \approx 19 \times 74 \approx 1400$ Ratio: $672 / 1400 \approx 6.7 / 14 \approx 0.47$. $0.47$ is closest to $0.4$. This confirms the answer rapidly. ### Common Pitfall Simply guessing $0.5$ because it feels like it's in the middle, and then panicking when $0.5$ isn't an option. You must look at the absolute numerical distance. $0.48$ is 8 units away from $0.40$, but 12 units away from $0.60$. It leans slightly toward $0.4$. ### Final Answer **Therefore, the correct answer is 0.4.**
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