Two cars leave from the same location but travel in opposite directions. The first car travels an average of 50 mi/hr and leaves 15 min before the second car, which travels an average of 55 mi/hr. How long each car travel before they are 200 mi apart?

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Answer 1 · 2016-04-27T09:41:29

1.79 hours

If we define the time t=0 as when the second care leaves.

Before the second care leaves, the first car travels a distance of:
#0.25 times 50"mi/hr"=12.5"mi"#
(since 15min = 0.25hr)

The total distance car 1 travels will be:
#=12.5 +50*t#

And car 2 travels a distance in the opposite direction:
#=55*t#

The total distance between them will be:
#12.5+50*t+55*t=12.5+105*t#

We want to know t when this equals 200 miles. So:

#12.5+105t=200#

Solving for t:

#105t=200-12.5=187.5#
#t=1.79 hrs#