Chemistry
posted by Shoaib .
A car tyre has a volume of 10 L when inflated. The tyre is inflated to a pressure of 3 atm at 17°C with air. Due to driving, the temperature of the tyre increases to 47°C.
a) what would be the pressure at this temperature?
b) how many litres of air measured at 47°C and pressure of 1 atm should be let out to restore the tyre to 3 atm at 47°C?

a.
(P1/T1) = (P2/T2)
b.
(P1V1/T1)= (P2V2/T2) 
I still am confused about the part B of the question. plz explain

I am too, but try this.
PV = nRT and plug in 3.31 atm, 10L, 320 K, and calculate n. That will be the number of moles at 290K as well as at 320 K. Then redo PV = nRT using 320K, 3 atm, then subtract moles at 3.31 atm from moles at 3 atm. That will be the moles that must be released. Then PV = nRT and plug in the new conditions for air to ber released. If I didn't goof the volume to be released is about 3 L *(@ 47 C and 1 atm P). 
Yea it works. we get 3.1 litre. thanks a lot..