a body Run for 10 minutes at a uniform speed of 9 km per hour at what speed should he Run for next 20 minutes so that the average speed comes to 12 km per hour
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Distance covered in 10 minutes = 9 kmph* 10/60 hrs = 1.5 km
Speed for the 2nd leg = V kmph
Distance coveed in 2nd leg = V * 20/60 = V / 3 km
Overall average speed = total distance / total time =
( 1.5 + V/3 ) / (10+20)/60 = 12 km/h
2 (1.5 + V/3) = 12
1.5 + V/3 = 6
V = 13.5 Km/h
Speed for the 2nd leg = V kmph
Distance coveed in 2nd leg = V * 20/60 = V / 3 km
Overall average speed = total distance / total time =
( 1.5 + V/3 ) / (10+20)/60 = 12 km/h
2 (1.5 + V/3) = 12
1.5 + V/3 = 6
V = 13.5 Km/h
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