Question

Two cars travel at the same speed to different destinations. Car A reaches its destination in 25 minutes. Car B reaches its destination in 35 minutes. Car B travels 4 miles farther than Car A. How fast do the cars travel?

Answer 1

Explanation:

speed = distance / time

distance = speed × time

they both have the same speed.

distanceB = distanceA + 4

so,

distanceA = speed × 25 min

distanceB = distanceA + 4 = speed × 35 min

distanceA = speed × 35 - 4

both distanceA expressions must be equal :

speed × 25 = speed × 35 - 4

subtract 25speed from both sides

0 = speed × 10 - 4

add 4 to both sides

4 = speed×10 min

divide both sides by 10 min

4 miles / 10 min = speed

to get the usual miles per hour, we need to multiply numerator and denominator by the same number, so that the denominator is 1 hour = 60 minutes.

as we cab see, we need to multiply by 6/6 :

4/10 × 6/6 = 24/60 = 24 miles per hour.