Question

A boy runs for 20 min. at a uniform speed of 18km/h. At what speed should he run for the next 40 min. so that the average speed comes 24km/hr.

Answer 1

Hey mate,....

1st case. d=vt

20min=1/3=0.3h, 0.3*18= 5.4km.

2nd case

40min=2/3=1.5h

1.5*d2

24= 5.4+d2/ 1.8h

43.2-5.4=d2

37.8=d2

** 12=37.8+ 5.4/1.8

12=43.2/1.8

12=24

2kmh^-1= speed of the the 2nd case..

Hope it will help you

Answer 2

20min=1/3=0.3h, 0.3*18= 5.4km.

40min=2/3=1.5h

1.5*d2

24= 5.4+d2/ 1.8h

43.2-5.4=d2

37.8=d2

** 12=37.8+ 5.4/1.8

12=43.2/1.8

12=24

2kmh^-1= speed of the the 2nd case..