Calculating Pressure at Different Altitudes and Depths

[robertsa]

Homework Statement

A mountaineer in the Rockies measures the air pressure to be 10% below that at sea level. At what height above sea level does he make the measurement? At this altitude he finds a small mountain lake of fresh water which is 4.3m deep at its deepest point. What is the pressure at the deepest point of the lake

Homework Equations

P-Po=density x g x distance?

The Attempt at a Solution

 

[rl.bhat]

Pressure at sea level = pressure due to 76 cm of mercury column.
10% less of this pressure is 68.4 cm of mercury column.
So the pressure at the mountain is ρ*g*h'. ρ is the density of the mercury.

 

[davidkis]

For the 2nd part P = D*G*H. density of water = 1000kg/m^3. After you get the pressure you simply add the atmospheric pressure. P = Pg + Pa. Make sure your units are correct, throws me off a lot.