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2014-10-31T12:02:17+05:30

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Let distance between home to school = x km
average speed while going = 20 km/h
time taken (t₁) = (x/20) h
average speed while returning = 30 km/h
time taken (t₂) = (x/30) h
total distance = x+x = 2x
total time = (x/20) + (x/30) = x(1/20 + 1/30) = x[(3+2)/60] = x(5/60) = x/12 h

Average speed = total distance/ total time taken
                       =2x/(x/12)
                       =(2x/x)×12
                       = 24 km/h
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2014-10-31T15:07:14+05:30

This Is a Certified Answer

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Certified answers contain reliable, trustworthy information vouched for by a hand-picked team of experts. Brainly has millions of high quality answers, all of them carefully moderated by our most trusted community members, but certified answers are the finest of the finest.
So let the distance to school be x 
so time taken to go school = x/20 hr
and time taken to return home = x/30 

total time = x/20 + x/30 = x/12
so total distance = x + x = 2x 

so average speed = 2x / x/12 = 2 x 12 = 24 km/h
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