math
posted by renjith .
On a journey across munbai,a taxi average 20mph for 76% of distance,25 mph for 10% of distance and 8 mph for remainder.then average speed of whole journey is?

so if the total distance is x miles, then the partial distances are :
.76x , .1x and .14x
the 3 different times are:
.76x/20 , .1x/25 , and .14x/8
avg speed = total distance/total time
= x/(x (.76/20 + .1/25 + .14/8) )
= 1/(.038 + .004 + .0175)
= 1/.0595
= appr 16.8 mph
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