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05/01/2021 5:02 pm
Topic starter
Abdul, while driving to school, computes the average speed for his trip to be 20 km h-1. On his return trip along the same route, there is less traffic and the average speed is 30 km h-1 What is the average speed for Abdul’s trip?
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05/01/2021 5:47 pm
Let the school be at a distance of x km. If t is time taken to reach the school, then
t1 = \(\frac{distance}{average\;speed}\)= \(\frac{x}{20}\)
If t2 is time taken to reach back, then
t2 = \(\frac{distance}{average\;speed}\)= \(\frac{x}{30}\)
Total time,
t = t1 + t2 = \(\frac{x}{20}\) + \(\frac{x}{30}\) = x[\(\frac{1}{20}\) + \(\frac{1}{30}]\) = \(\frac{5x}{60}\) = \(\frac{x}{12}\)
Total distance x + x = 2x
Average speed = \(\frac{total\;distance}{total\;time}\)
= \(\frac{2x}{x/12}\)
= 24 km h-1