Question
A motor-cycle covers 140 km with a speed of 40 km/hr.
find the speed of the motor-cycle for the next 140 km journey so that the average speed of the whole journey will be 55 km/hr.Solution
Average speed of whole journey = 55 km/hr Using the formula, average speed = 2xy/(x + y) rArr; x = speed of first 140 km = 40 km/hr rArr; 55 = 2 times; (40 times; y)/(40 + y) rArr; 88 km/hr
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