Question

By what rational number should $\frac{-3}{5}$ be multiplied to obtain $21$?

• A. $\frac{507}{4}$
• B. $35$
• C. $-35$
• D. $507$

Answer 1

The correct option is C $-35$

Let us assume the number be $x$

that should be multiplied by $\frac{-3}{5}$ to obtain $21$

Now making an equation for this

$\frac{-3}{5}\times x=21$

$\Rightarrow \frac{-3x}{5}=21$

$\Rightarrow -3x=21\times 5$

$\Rightarrow -3x=105$

$\Rightarrow x=\frac{105}{-3}=-35$