I need this answered for college.

Question

A truck enters a highway driving 60 mph. A car enters the highway at the same place 7 minutes later and drives 65 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

Rate x Time = Distance

 

truck speed = 60 mph

 

time for the truck = T

 

truck distance = 60T

 

car speed = 65 mph

 

car time = T - 7 min.

 

car distance = 65 ( T - 7/60 )      

 

time must be in hours because speed is mph

 

the two distances are equal:

 

    60T = 65 (T - 7/60)

 

    60T = 65T - (7(65)/60

 

    -5T = -7(13/12)

 

       T = [-7(13/12)/-5]

 

       T = 1.51 hrs.

 

It will take just a little more than 1 1/2 hours to pass

Answer 2

d = r · t

d = 60(t + 7/60)

d = 65t

 

60(t + 7/60) = 65t

60t + 7 = 65t

7 = 5t

7/5 = t

 

The car passes after one hour and twenty-four minutes.