An express train takes 1 hour less than a passenger train to travel 132 km between Mysore and Bangalore (without taking into consideration the time they stop at intermediate stations). If the average speed of the express train is 11km/h more than that of the passenger train, find the average speed of the two trains.

NCERT Class X
Mathematics - Mathematics

Chapter _QUADRATIC EQUATIONS

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Answers

2015-06-10T06:28:11+05:30
Let speed of passenger train be x km/hr

So, according to the problem,
132/x - 132/(x+11) = 1
or, 132*11 = x2 + 11x
or, x2 + 11x - 1452 = 0
or, x2 + 44x - 33x - 1452 = 0
or, (x+44)(x-33) = 0
or, x = 33 (x cannot be negative)
So, speed of express train is 33+11 km/hr = 44km/hr
So, avg speed = (33+44)/2 km/hr = 38.5 km/hr

Answer: - Average speed of the 2 trains are 38.5 km/hr
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