Question 656174

From a point on a straight road, two cars are driven in opposite directions, one at 21 miles per hour and the other at 20 miles per hour. In how many hours will they be 164 miles apart?


Distance (D) = speed (S) or rate (R) , times time (T)
D = S * T ----- T = D/S


In this case, S, or speed = sum of the two vehicles' speeds


Therefore, T, or time = 164/(21 + 20)


OR


Distance traveled by faster vehicle, plus distance traveled by slower vehicle equals distance that both vehicles are apart, after a certain period of time


This results in: 21T + 20T = 164. Solve for T, and you have the time.


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