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Car A began a journey from a point at 9 am, traveling at 30 mph. At 10 am car B started traveling from the same point at 40 mph in the same direction as car A. At what time will car B pass car A?
 

 Apr 4, 2017
 #1
avatar+129850 
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We can use logic here :

 

Note that when Car B started......Car A has already traveled 30 miles.......so.....Car B must make up a 30 mile gap

 

And the difference in speeds  is  40 - 30  = 10 mph

 

So.....Car B  makes up a 10 mile gap every hour.....so.....it must take Car B  3 hours to catch Car A, i.e, at  1 PM

 

 

cool cool cool

 Apr 4, 2017
 #2
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+1

Let time = t,  Speed = Distance/Time. Then we have:

30(t+1) =40t, solve for t

t =3 hours - or about 1:00 pm, when car B catches up with car A.

 Apr 4, 2017

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