At constant temperature, a gas is at a pressure of 940 . 3mmHg ....

From Boyle's Law,

${P}_{2}{V}_{2} = {P}_{1}{V}_{1}$

${P}_{1} = 940 . 3$ mm of $Hg$

${P}_{2} =$ Pressure at which volume is reduced by $40$

${V}_{2} =$ Volume decreased by $40$

\left({V}_{2} = {V}_{1} - 0 . 4{V}_{1} = 0 . 6{V}_{1}\right)$</p><p>Then,${P}_{2} = \dfrac{940 . 3 \times {V}_{1}}{0 . 6{V}_{1}}$</p><p>$= 1567 . 16$</p><p>$\approx 1567mmHg