College Algebra

Question

It takes John 40 minutes to drive to work, it takes him 30 minutes if he takes the train. How many miles does John travel to work if the train is moving 15 miles an hour faster than the car.

Answer 1

c = speed of car

c + 15 = speed of train

 

d = s · t

d = c(2/3)              40minutes is 2/3 of an hour

d = (c + 15)(1/4)    15 minutes is 1/4 hour

 

c(2/3) = (c + 15)(1/4)

2c/3 = c/4 + 15/4

8c/12 = 3c/12 + 15/4

5c/12 = 15/4

5c = 180/4

c = 36/4

c = 9

 

John travels 2/3 hour at 9 mph or 6 miles