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.

Question

Mathematics

Julian White

6 April, 10:41

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.

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Answers (1)

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Caden · 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