Question

By what number should ${\left(15\right)}^{-1}$ be multiplied so that the product may be equal to ${(-5)}^{-1}$?

Answer 1

Let the required number be $x$.

$\therefore (15{)}^{-1}\times x=(-5{)}^{-1}$

$\Rightarrow \frac{1}{15}\times x=\frac{-1}{5}$

$\Rightarrow x=\frac{-15}{5}$

$\therefore x=-3$

Hence, the required number is $-3$.