At what altitude above sea level atmospheric pressure can be considered normal, equal to: a) 670 mm; b) 790mm?

The standard atmospheric pressure at sea level is 760 mm Hg. Art.
a) For every approximately 10.5 meters above sea level, the pressure drops by 1 mm Hg. Art. Let’s calculate what is the difference between normal atmospheric pressure and 670 mm Hg. Art .: 760 – 670 = 90 mm Hg. Art.
Since the pressure dropped by 90 mm Hg. Art., then the height above sea level changed to: 90 * 10.5 = 945 (m).
Thus, the height at which the pressure is 670 mm Hg. Art. can be considered normal, equal to 945 m above sea level.
b) When descending below sea level, the opposite situation occurs: descent for every 10.5 m leads to an increase in atmospheric pressure by 1 mm Hg. Art .: 760 – 790 = – 30 mm Hg. Art.
Since the pressure increased by 30 mm Hg. Art., then the location compared to sea level changed by: – ​​30 * 10.5 = – 315 (m).
Thus, the pressure is 790 mm Hg. Art. can be considered normal when located 315 m below sea level.
Answer: a) 945 m; b) – 315 m.