What is the atmospheric pressure at the top of a mountain 3 km high, if at the foot it is 750 mm Hg?

With altitude, atmospheric pressure decreases, since the higher, the less the air thickness, therefore, the lower the atmospheric pressure. For every 1000 m, the pressure decreases by 100 mm. If the pressure at the foot is 750 mm, then at an altitude of 3000 m, i.e. 3 km, it will be 450 km.

1000 m-100 mm

3000 m – x mm

x = 3000 x 100/1000

x = 300 mm

750 – 300 = 450 mm