At constant temperature, a gas is at a pressure of 940.3 mm Hg. The pressure at which its volume decreases by 40% is _______ mm Hg. (Nearest integer)

At constant temperature, Boyle’s law applies: $$P_1V_1 = P_2V_2$$. Here $$P_1 = 940.3$$ mm Hg and since the volume decreases by 40%, $$V_2 = 0.6V_1$$.

Substituting gives $$940.3 \times V_1 = P_2 \times 0.6V_1$$, so $$P_2 = \frac{940.3}{0.6} = 1567.17 \approx 1567 \text{ mm Hg}$$. Therefore, the pressure is 1567 mm Hg.