InterviewSolution
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A car travels from A to B at a speed of 20 km h-and returns at a speed of 30 km h-'. The averagespeed of the car for the whole journey is(A) 5 km h-(B) 24 km h-(C) 25 km h-(D) 50 km h-10. |
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Answer» C) is the correct answer is ( d). 50 is the correct answer Hii frnd.. the speed average is Total average speed is simply = Total distance/Total timeLets say,D = distance travelled by the car in EACH directiont1 = time spent on onward tript2 = time spent on return tripThus, the total distance travelled by the car = D+D= 2DAnd, by the formula, Speed = Distance/TimeS1 = D/t1 => t1 = D/S1S2 = D/t2 => t2 = D/S2Total average speed = Total Distance/Total time = 2D/(t1+t2) = 2D/(D/S1+D/S2) = 2S1*S2/(S1+S2) Remember this general formula for a total average speed problems:Total average speed = 2S1*S2/(S1+S2) So in the question S1 = 20km/hr &S2 = 30km/hr So av. speed = 2 x 20 x 30/20+30 = 24km/hr 24km / hr is the right answer please accept best 25 is the right answer option b is right answer |
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