Question 27210: Two cars start at an interstate interchange and travel in the same direction at average speeds of 40 mph and 55 mph. How much time must elapse before the two cars are 5 miles apart?
Answer by JayJay_T(6)   (Show Source):
You can put this solution on YOUR website! Let 'x' be the time you want to know. Therefor:
40[m/h].x[h] + 5[m] = 55[m/h].x[h]
This means that after a certain time 'x', the 1st car has travelled a
distance 40[m/h].x[h] The question was the exact time at which the 2nd car was 5 miles ahead. So you take the distance of the first car 40[m/h].x[h], and add the 5 miles. This should be equal to the distance of the 2nd car (55[m/h].x[h])
=> 40x+5=55x
=> 5 = 15x
=> x = 1/3 or in this case, 1/3 of an hour, being 20 minutes.
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