Word problem

Question

One car traveled an average 7 mph faster than the other. When the first car arrived at the destination after 5 1/2 hours of driving, both cars driven 600 miles. If the second car continues at the same average speed, how much time to the nearest minute before the second car arrives?

Answer 1

The distance formula is:  distance = rate*time, or d=rt

 

If the slower car drives at r mph

The faster car drives r+7 mph

 

600 = (r+7)5.5     distance = rate*time

From this we can find the rate of speed, r, which will tell

us how fast the slower car is driving.

 

600 = 5.5(r+7)

600 = 5.5r + 38.5

5.5r = 600 - 38.5

5.5r = 561.5

r = 561.5/5

r = 102.091 mph

 

This is the speed at which the slower car is driving.

***These guys are moving pretty quick... lol***

 

Plug that into the distance formula to find the driving

time for the slower car

 

600 = 102.091(t)

t = 600/102.091

t = 5.8771 hours

 

The faster car took 5.5 hours, the slower car took 5.8771 hours.

The time difference in arrival is 5.8771-5.5 = .3771 hours

 

(.3771 hours)(6o minuts/hour) = 22.626 mins

 

Rounded to the nearest minute, the 2nd car will arrive 23 mins after the first.