Question

Mark the correct alternative in each of the following:

If $\frac{-3}{7}=\frac{x}{35}$, then x =

(a) 15 (b) 21 (c) −15 (d) −21

Answer 1

Firstly, write $\frac{-3}{7}$ as a rational number with denominator 35.

Multiplying the numerator and denominator of $\frac{-3}{7}$ by 5, we have

$\frac{-3}{7}=\frac{-3\times 5}{7\times 5}=\frac{-15}{35}$

$$\begin{gathered} \therefore \frac{-3}{7}=\frac{x}{35} \\ \Rightarrow \frac{-15}{35}=\frac{x}{35} \\ \Rightarrow x=-15 \end{gathered}$$

Hence, the correct answer is option (c).