SOLUTION: The approximate distance above sea level,d, in kilometres, is given by the formula d= (400(log(P/2)-2.5))/30, where P is the barametric pressure in kilopascals(kPa). What is the ba

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons -> SOLUTION: The approximate distance above sea level,d, in kilometres, is given by the formula d= (400(log(P/2)-2.5))/30, where P is the barametric pressure in kilopascals(kPa). What is the ba      Log On


   

Question 138583: The approximate distance above sea level,d, in kilometres, is given by the formula d= (400(log(P/2)-2.5))/30, where P is the barametric pressure in kilopascals(kPa). What is the barometric pressure 12 kilometres above sea level? PLEASE HELP ME :)
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
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The approximate distance above sea level,d, in kilometres, is given by the formula d= (400(log(P/2)-2.5))/30, where P is the barametric pressure in kilopascals(kPa). What is the barometric pressure 12 kilometres above sea level?
:
Substitute 12 for d in the formula
%28400%28log%28%28P%2F2%29%29-2.5%29%29%2F30 = 12
:
Multiply both sides by 30 to get rid of the denominator
400(log(p/2)) - 2.5 = 30 * 12
:
400(log(p/2)) - 2.5 = 360
:
Divide both sides by 400:
log(p/2) - 2.5 = 360%2F400
log(p/2) - 2.5 = .9
:
Add 2.5 to both sides:
log(p/2) = .9 + 2.5
log(p/2) = 3.4
:
Find 10^x of both sides
p%2F2 = 2511.8864
Multiply both sides by 2
p = 2511.8864 * 2
:
P = 5023.77 kPa
:
:
Check solution on calc; enter:(400(log(5023.77/2)-2.5))/30 = 11.9999 ~ 12