how long will it take the car to pass the truck?

Question

a truck enters a highway driving 60 mph. a car enters a highway at the same place 12 minutes later and drives 72 mph in the same direction. from the time the car enters the highway how long will it take the car to pass it?

Answer 1

Hi Jaicee,

The car will start to pass the truck when both vehicles have covered the same distance.

Let t = time (in hours) it takes for the car to start to pass the truck.

distance = rate x time, so

for the truck, d = 60mph x [(12min/60min per hr)+t]

for the car, d = 72mph x t

Since the distances are equal, 60 x (0.2+t) = 72 x t

Solve for t.

12+60t = 72t

12 = 12t

t = 1hr.

Answer 2

Hi Jaicee,

 

Let x = time in minutes it takes the car to catch the truck

 

we know that distance = speed * time 

 

in this case we want the distance of the car and truck to be the same

 

so

 

60 * (x+12) /60  = 72 * x/60    (added 12 to the truck's time because it started 12 minutes sooner

 

x +12 = 1.2x

 

12 = .2x

 

60 = x                             (the car will catch the truck in 60 minutes , it will begin to pass the truck in the next minute

 

Hope this helps