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100.A train covers the first half of the distance betweentwo stations at a speed of 40 km/h and the otherhalf at 60 km/h. Then its average speed is -(1) 50 km/lh(3) 52 km/h(2) 48 km/h(4) 100 km/h |
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Answer» Let the total distance be D now time taken to cover first half =( D/2)/(40)and time taken to cover 2nd half = (D/2)/(60) total time taken = D/80 +D/120 = 5D/240 = D/48 so, avg. speed = distance/(time) = D/(D/48) = 48km/h I have done that same thing in shorter time with help of formula 2.v1.v2/v1+v2 |
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