Question

2 Two cars left the city for a suburb, 480 km away, at the same time. The speed of one of the cars was 20 km/hour greater than the speed of the other, and that is why it arrived at the suburb 2 hour earlier than the other car. Find the speeds of both cars.

Answer 1

80 km

60 km

Step-by-step explanation:

Remember that; time = distance/ speed

Assume that the first car is traveling at x km/h

The second is traveling at (x+20) km/h

The distance is given as 480km

The difference in their arrival is 2hrs. Therefore;

480/x – 480/(x+20) = 2

480(x+20) – 480x = 2x(x+20)

480x + 9600 - 480x = 2x² – 40x

2x² - 40x - 9600 = 0

2x² + 120x – 160x - 9600 = 0

2x (x - 60) - 160 (x -60 ) = 0

(2x – 160) (x - 60) = 0

2x - 160 = 0

x = 80

x - 60 = 0

x = 60