A boy runs for 10 minutes at a uniform speed of 18 km per hour. At what speed should he runs for the next 20 minutes so that the average speed becomes 12 km per hour?

Q. An automobile driver travels from plane to a hill station 120 km distant at an average speed of 30 km per hour. He than makes the return trip at an average speed of 25 km per hour. He covers another 120 km distance on plane at an average speed of 50 km per hour. His average speed over the entire distance of 360 km will be

Q. Aaron will jog from home at

x

miles per hour and then walk back home by the same route at

y

miles per hour. How many miles from home can Aaron jog so that he spends a total of t hours jogging and walking?

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Melwin jogs 18 km at a speed of 12 km per hour. At what speed would he need to jog during the next 3 hours to have an average of 18 km per hour for the entire jogging session?

The correct option is E 21 kmph Let the distance Melwin needs to cover in 3 hrs be 'x'. Average speed = Total distanceTotal time ⇒ 18 = 18+x3+1812 ⇒ 81 = 18 + x ⇒ x = 63 kms So, Melwin has to run 63 kms in 3 hrs. So, Melvin's speed for the next 3 hrs = 21 kmph