MATH PLEASE HELP!
posted by Roger .
According to Boyle's law, the pressure p of a compressed gas is inversely proportional to the volume, v. If a pressure of 20 pounds per square inch exists when the volume of the gas is 500 cubic inches, what is the pressure when the gas is compressed to 400 cubic inches?

P = k/V
when P=20, V=500, so
20 = k/500
k = 10000
then P = 10000/V
if V  400,
P = 10000/400 = 25
don't forget the units 
PROOF: 2/LOG A BASE 9  1/ LOG A BASE 5 = 3/ LOG A BASE 3

thanks but how did you get 1000 by dividing k by 500?

I had 20 = k/500
now multiply both sides by 500
20(500) = (k/500)(500
10000=k
the 500's canceled on the right side 
thank you so much! i really appreciate it!