posted by Cathy .
I am working with a graph and if at every 5.6 km you cut in half the atmospheric mass. So at 16.8 km wouldn't you have 12.5% of the atmosphere above and 87.5% would be below?
16.8 = 5.6 x 3, so the mass above 16.8 km decreases to (1/2)^3 = 1/8 or 12.5% of its sea level value.
Your answer is correct