a truck enters a hwy

Question

a truck enters a highway driving 60 mph. a car enters the highway at the same place 10 minutes later and drives 74 mph in the same direction. from the time the car enters the highway, how long will it take the car to pass the truck

Answer 1

Let's let t be the time, measured from when the car enters the highway.

 

The distance the car travels would be 74 t.

 

The distance the truck travels from that time would be 60 (t + 1/6).  You add 1/6 because the truck had 10 extra minutes, which is equal to 1/6 of an hour.  We have to use hours because the speeds are given in miles per hour.

 

When the car passes the truck, their distances will be the same, so set these two distance expressions equal to each other.

 

74t = 60 (t + 1/6)

74t = 60t + 10

14t = 10

t = 10/14

 

So the time it takes the car to pass the truck is 10/14 hour, or around 42.9 minutes.