Mark (✓) against the correct answer:

(b) 15%

Let the required number be $\mathrm{x}$. Then, we have :

$(x \%$ of 320$)=48$

$\Rightarrow\left(320 \times \frac{x}{100}\right)=48$

$\Rightarrow \frac{320 x}{100}=48$

$\Rightarrow x=\left(48 \times \frac{100}{320}\right)$

$\Rightarrow x=15 \%$