Question 88790
The average speed of a train is 20 miles per hour faster than that of a car.In 8 hours and 40 minutes , the train covers the same distance that the car covers in 13 hours . Find the average speed of each .
:
Let s = speed of the car
Then
(s+20) = speed of the train
:
Change 8 hr 40 min to hrs: 8 + 40/60 = 8 & 2/3 hrs or 26/3 hrs
:
Distance = time * speed
:
car dist = train dist
13s = {{{(26/3)(s+20)}}}
:
Mult equation by 3, get rid of the denominator:
3(13s) = 26(s+20)
:
39s = 26s + 520
:
39s - 13s = 520
;
13s = 520
:
s = 520/13
:
s = 40 mph is the speed of the car
:
60 mph is the speed of the train
:
:
Check:
13*40 = 520
8&2/3 * 60 = 520 mi also