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
-
A0.2
-
B0.4
-
C0.6
-
D1
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.**