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Abdul, while driving to school, computes...

Abdul, while driving to school, computes the average speed for his trip to be `20 kmh^(-1)` on his return trip along the same route, there is less traffic and the average speed is `40kmh^(-1)`. What is the average speed for Abdul's trip?

Text Solution

Verified by Experts

The distance Abdul comutes while driving from home to school = S
Let us assume time by Abdul to comutes this distance = `t_(1)`
Distance Abdul comuntes while driving from school to Home= S
Let us assume time taken by Abdul to commutes this distance =`t_(2)`
Average speed from home to school `V_(1) av = 20khm^(-1)`
Average speed from school to home `V_(2) av = 30kmh^(-1)`
Also we know time taken from school to Home `t_(2) = S//V_("1av")`
Similarly Time taken from school to home `t_(2) = S//V_("2av")`
Total distance from home to school and backward = 2s
Total time taken from home to school and backward = S/20 + S30
Therefore, Average speed (Vav) for covering total distance (2S) = Total distance/Total time
`=2s//(S//20 + S//30)`
`=2S//[(30s + 20s)]//600]`
=1200s/50s
`=24 kmh^(-1)`
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