Question

A boy runs 5 minutes at a uniform speed of 10 km/hr. At what speed should he run for the next 10mins so that the average speed comes to 12km/hr?

Answer 1

Explanation:

5mins 10km/hr

distance=5/60×10=5/6=0.833

required 15mins 12km/hr

distance(total)=15/60×12

=1/4×12

=3km

distance he should cover in 10mins=1/6×x

distance=3-0.833=2.166

=13/6km

13/6=1/6×x

x=13/6×6

x=13

Answer 2

Answer:

3

Explanation:

time =5 minutes =5/60=1/12hr

speed=10km/hr

distance=speed*time

distance = 10*5/60=5/6

time=10 minutes =10/60=1/6

distance=speed*time

distance=speed 1/6

total distance= 5/6+speed/6=5+speed/6

total time=1/12+1/6=1/4

average speed=total distance /total time

12=5+speed/6/1/4

speed=3