Question

a car travelled 30km at uniformed speed of 40kmper hour and the next 30km at the uniform speed of 20kmper hours find the average speed .
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Answer 1

given that ,

    1st 30 km uniform speed is (u1) = 40 km/h 

     2nd 30 km uniform speed is ( u2 ) = 20 km/h

     total distance ( d ) = 30 + 30 = 60 km

     time taken in 1st time = d / t = 30/40 also, 3h / 4 = 180/4 = 45 min

     tim taken in 2nd time = d/t = 30/20 also, 3h/2 = 180/2 = 90 min

    total time = 45 + 90 = 135 min = 135/60 h

av.speed = 60/135/60 = 60 * 60 /135 = 26.66 km/h ( answer )

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