Question 78797

Let's let the independent variable be d = depth in feet and the pressure is P(d) in KPa.

The information given is P(0) = 101.3 and (seems like) P is a linear function and the slope is 29.9/10.

So it looks like P(d) = 101.3 + 2.99 d

There is no other info in the problem to correct for the curvature of the earth, the decreasing distance to the center of the earth, the changing density of the water due to temperature, perturbations due to shark fins etc. so the statement of linearity is a reasonable assumption to make given the available information.

All you gotta do is solve 101.3 + 2.99d = 690

2.99d = 690 - 101.3 = 688.7

d = 688.7 / 2.99 = 230.34448160535 (according to javascript)
d ~= 230.3 to 1 significant decimal place.