Question

Find the value of $7^{-3}$.

• A. $343$
• B. $\frac{1}{343}$
• C. $\frac{1}{21}$
• D. $\frac{1}{49}$

Answer 1

The correct option is B

$\frac{1}{343}$

We know that $a^{-m}=\frac{1}{a^m}$ for any non-zero integer $a$ and integer $m.$
$⟹7^{-3}=\frac{1}{7^3}$
$=\frac{1}{7\times 7\times 7}=\frac{1}{343}$