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22/10/2021 6:21 pm
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A motorcyclist drives from place A to B with a uniform speed of 30 km h-1 and returns from place B to A with a uniform speed of 20 km h-1. Find his average speed.
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22/10/2021 6:30 pm
Speed from A to B = 30 km/h
Let the distance from A to B be D.
Time taken to travel from A to B, T1 = \(\frac{Distance \;travelled}{Speed}\)
T1 = \(\frac{D}{30}\)
Speed from B to A = 20 km/h
Time taken to travel from B to A, T2 = \(\frac{Distance \;travelled}{Speed}\)
= \(\frac{D}{20}\)
Total time taken, T = T1 + T2
= \(\frac{D}{30}\) + \(\frac{D}{20}\) = \(\frac{D}{12}\)
Total distance from A to B and from B to A = 2D
Average speed = \(\frac{Total\; distance \;travelled}{Total\;time\;taken}\)
= \(\frac{2D}{\frac{D}{12}}\) = 24 km/h
This post was modified 4 years ago by Mayank1444