Asked by Stacy
The distance between towns A and B is 280 km.A car and a lorry travel from A to B.The average speed of the lorry is 20km/hr less than that of the car whose speed is x km/hr.The lorry takes 1h and 10 minutes more than the car to travel from A to B.Write an expression in terms of x for the time taken to cover 280km by:a)car b)lorry
Answers
Answered by
Reiny
speed of car ---- x km/h
speed of lorry -- x-20 km/h
time taken by car = 280/x hrs
time taken by lorry = 280/(x-20) hrs.
1 hour and 10 minutes = 1 + 10/60 = 7/6 hrs
280/(x-20) - 280/x = 7/6
multiply each term by 6x(x-20)
280(6x) - 280(6(x-20)) = 7x(x-20)
expand, arrange as a quadratic and solve using your favourite method.
speed of lorry -- x-20 km/h
time taken by car = 280/x hrs
time taken by lorry = 280/(x-20) hrs.
1 hour and 10 minutes = 1 + 10/60 = 7/6 hrs
280/(x-20) - 280/x = 7/6
multiply each term by 6x(x-20)
280(6x) - 280(6(x-20)) = 7x(x-20)
expand, arrange as a quadratic and solve using your favourite method.
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