Math IN URGENT NEED OF FEEDBACK
posted by Anonymous on .
If the temperature is constant, then the atmospheric pressure P (in pounds/square inch) varies with the altitude above sea level h in accordance with the law given below where p0 is the atmospheric pressure at sea level and k is a constant.
P = p0ekh
If the atmospheric pressure is 14.9 lb/in2 at sea level and 12.6 lb/in2 at 4000 ft, find the atmospheric pressure at an altitude of 13,000 ft. (Round your answer to two decimal places.)
For this question I got 8.65 as my answer but for some reason I keep getting it wrong. Can someone please explain what I'm doing wrong.

12.6=14.9k4000
k=2.3/4000
p=14.9(2.3/4000)*13000
p=7.43PSI recheck your calcs. 
You forgot e in the calculations. I put in your number, it's not right. I'm sorry to be such a pain but I can't figure this out.

p=14.9* e^(kh)
12.6=14.9 * e^(k4000) take ln of each side
ln(12.6)= ln(14.9)k4000
.168=k*4000
k=4.19E5
p=14.9 e^(4.19E5*13000)=14.9 e^(.5447)
p=8.65 PSI 
Yeah, that's what I got too, but I keep getting the problem wrong. Don't worry about it though, I'm going to contact my professor and ask her what's going on. Thanks

The atmospheric pressure P in pounds per square inch (psi) is given by
P = 14.7 e−0.21 a
where a is the altitude above sea level (in miles). If a city has an atmospheric pressure of 11.39 psi, what is its altitude? (Recall that 1 mi = 5,280 ft. Round your answer to the nearest foot.)
Incorrect: Your answer is incorrect. ft