80 km
60 km
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