Question 315526
It took John 12 hours riding his bike to make the round trip to his uncle's.
 If he averaged 20 mph out and 30 mph back, how long did he travel each way? 
:
Let d = dist traveled one way
Write a time equation; time = dist/speed
{{{d/20}}} + {{{d/30}}} = 12
multiply eq by 60, results
3d + 2d = 60(12)
5d = 720
d = {{{720/5}}} = 144 mi one way
:
Find the time at each speed
{{{144/20}}} = 7.2 hrs at 20 mph
{{{144/30}}} = 4.8 hrs at 30 mph