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A car passes point A driving at a constant rate of 60 km/h. A second car, traveling at a constant rate of 75 km/h, passes the same point A a while later and then follows the fist car. It catches the first car after traveling a distance of 75 km past point A. How many minutes after the first car passed point A did the second car pass point A?

 Jan 7, 2020
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Call D  the distance  that the first car is from point A when the second car passes point A

 

Then the remaining  time for the  first car  to  travel 75 miles from point A  must be 

 

(75 - D)  / 60

 

And since the second car catches the first car 75 km  past point A  and it travels at  75km/h it must take this car 1 hour to  catch the  first car after passing point A

 

So.....the time it takes the first car to travel (75 - D) km   must be just  1 hour

 

So

 

(75 - D) / 60  = 1 

 

D =  15

 

So...the first car is 15 km past point A when the second car reaches point A

 

So.....the time it takes the  first car to travel 15 km =  15 minutes

 

So......the second car must pass point A 15 minutes after the  first

 

 

 

cool cool cool

 Jan 7, 2020
edited by CPhill  Jan 7, 2020
edited by CPhill  Jan 7, 2020

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