Explanation

(b) At constant temperature,
$p_{1}V_{1} = p_{2}V_{2}$
Or $\frac{p_{1}}{p_{2}} = \frac{V_{2}}{V_{1}}$
Fractional change in volume
$\frac{V_{1} - V_{2}}{V_{1}} = \frac{4}{100} = \frac{1}{25}$
$1 - \frac{V_{2}}{V_{1}} = \frac{1}{25}$
$\frac{V_{2}}{V_{1}} = \frac{24}{25}$
$\therefore\ \ \frac{p_{1}}{p_{2}} = \frac{V_{2}}{V_{1}} = \frac{24}{25}$
or $\frac{p_{2}}{p_{1}} = \frac{25}{24}$
$\frac{p_{2} - p_{1}}{p_{1}} = \frac{25}{24} - 1 = \frac{1}{24}$
% increase in pressure $= \frac{100}{24} = 4.16\%$