<PRE><B>Question 1115599</B>
speed=v
v*time=distance
v*t=60
(v+5)*(t-1)=60, because one hour less time to go the same distance at 5 mph faster.
t=60/v
t-1=60/(v+5)
t=(60+v+5)/(v+5), common denominator
Set the two t s equal to each other
(60/v)=(60+v+5)/(v+5)
cross-multiply
60(v+5)=v(65+v)
60v+300=65v+v^2
0=v^2+5v-300
(v+20)(v-15)=0
v=15 mph only positive root, 4 hours to go 60 miles and 
3 hours to go 60 miles at 20 mph.

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