What is the atmospheric pressure at the top of the mountain if at its foot it is 765 mm of mercury.

What is the atmospheric pressure at the top of the mountain if at its foot it is 765 mm of mercury. the height of the mountain is 4 km.

To solve this problem, one should be guided by the basic rule of changing atmospheric pressure with increasing altitude. It is known that with a rise of every 10 meters, atmospheric pressure drops by 1 mm Hg. Hence, we can conclude that pressure will change as follows:
4000 ÷ 10 = 400 mm Hg
Now we can calculate what pressure will be at the top of the mountain. To do this, execute:
765 – 400 = 365 mm Hg
Thus, at the top of the mountain, the barometer will show 365 mm Hg.