Question

Car A travels 90 km in the same time car B going 10 km/hr slower travels 60 km. Find the speech of each. List answer for car A first then car B. Do not show units.

Answer 1

For

Car A : 30

Car B : 20

Explanation:

Let the speed at which Car A travels be x and the time of travel be T. Recall that

speed = distance/time

Hence for Car A.

x = 90/T

T = 90/x

since Car B is B going 10 km/hr slower travels 60 km then

T = 60/(x - 10)

equating both equations

90/x = 60/(x - 10)

cross multiply

90(x - 10) = 60x

90x - 900 = 60x

90x - 60x = 900

30x = 900

Divide both sides by 30

x = 900/30

= 30

This is the speed of Car A : 30km/hr

The speed of Car B = 30 - 10 = 20 km/hr