Question

a boy runs for 10 minutes at a uniform speed of 9 km per hour at what speed should he done for the next 20 minutes so that the average speed becomes to 12 kilometre per hour

Answer 1

Average speed = Total distance / Total time

D1 = 9 × 1/6 = 1.5 km

D2 = V2 × 0.33 = 0.33V2

Average speed =( 1.5 + 0.33V2)/1/2

12 = 2 (1.5 + 0.33V2)

6 = 1.5 + 0.33V2

6 - 1.5 = 0.33V2

4.5 / 0.33 = V2

V2 = 13.6Km/Hr



Thanks