Question

What is the number that is one half of one quarter of one tenth of 400?

• A. 2
• B. 5
• C. 8
• D. 10

Hint:

Work the divisions in order: tenth, then quarter, then half of the previous result.

Answer 1

The Correct Option is B

Instead of computing step by step, combine all three fractions into one multiplier first.

One half is $\frac{1}{2}$, one quarter is $\frac{1}{4}$, and one tenth is $\frac{1}{10}$. Multiplying these together gives the combined fraction of 400 that is required:

\[\frac{1}{2} \times \frac{1}{4} \times \frac{1}{10} = \frac{1}{80}\]

Now apply this single fraction to 400:

\[400 \times \frac{1}{80} = 5\]

This matches option (2). As a check, dividing 400 by 80 directly gives 5, with no room left for the smaller value 2 or the larger values 8 and 10 seen in the other options; those would require dividing 400 by 200, 50 or 40 instead, none of which equals $\frac{1}{2}\times\frac{1}{4}\times\frac{1}{10}$.

So the required number is \(\boxed{5}\).