Question

The average speed of an express train is 20km/hour more than the average speed of a passenger train .To cover a distance of 360kms the express train takes 3 hours less than that of the passenger train. Find the average speed of both passenger and express train.
speed of passenger train ---- x km/h
speed of express ------ x+20 km/h

Time = distance/rate

360/x - 360/(x+20) = 3 , saying the difference in their times is 3 hours

multiply each term by x(x+20), the LCD
360(x+20) - 360x = 3x(x+20)

3x^2 + 60x - 7200 = 0
x^2 + 20x - 2400 = 0
(x - 40)(x+60) = 0

carry on

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