Math
posted by Kelsey on .
I need help with this problem:
Two planes start from Los Angeles International Airport and fly in opposite directions. The second plane starts ½ hour after the first plane, but its speed is 80 kilometers per hour faster. Find the airspeed of each plane if 2 hours after the first plane departs the planes are 3200 kilometers apart.

distance slow plane=vt
distance fast plane=.5*(v+80)t +(v+80)t
3200=sum of the two distances, or
3200=v*2+.t(v+80)*2 + (v+80)*2
solve for v, then for the faster plane, its speed is v+80 
Whats 1/5 (one fifth) of 200?

40 times five is 200