Question

A boy runs for 10 mins at a uniform speed for 9 km/h. At what speed should he run for further 20 mins, so that his average speed is 12km/h?​

Answer 1

Answer:

9/10+x/20=12

(18+10x)/20=12

18+10x=240

10x=240-18

10x=222

x=222/10

x=22.2

22.2km/h