Question

A student instead of finding the value of $\frac{7}{8}$ of a number, found the value of $\frac{7}{18}$ of the number. If his answer differed from the actual one by 770, find the number.

• A. 1584
• B. 2520
• C. 1728
• D. 1656

Hint:

In fraction difference problems, subtract fractions first before multiplying by the number.

Answer 1

The Correct Option is B

Let number = $x$. $\frac{7}{8}x - \frac{7}{18}x = 770$ $\Rightarrow 7x \left( \frac{1}{8} - \frac{1}{18} \right) = 770$ $\Rightarrow 7x \left( \frac{18 - 8}{144} \right) = 770$ $\Rightarrow 7x \cdot \frac{10}{144} = 770$ $\Rightarrow \frac{70x}{144} = 770 \Rightarrow x = 2520$.