Question

A man covers a distance of 40km.He covers first 10km at 10km/h, second 10 km at
20km/h, third f Okm at 30km/h and last 10km at 40km/h. What is the average speed of
man?

Answer 1

Answer:

average speed = 19.5 km/hr

Step-by-step explanation:

total distance covered = 40 km

first case,

distance covered = 10km

speed = 10km/h

time = distance / speed

t=10/10

t=1 hr .........(i)

second case,

distance travelled by him = 10km

speed = 20km/hr

time=distance/speed

t=10/20

t=0.5 hr .........(ii)

third case,

distance travelled = 10 km

speed=30 km/hr

time=distance/speed

t=10/30

t=1/3

t=0.3 hr ...........(iii)

fourth case,

distance travelled = 10 km

speed = 40 km/hr

time= distance/speed

t=10/40

t=0.25 hr .........(iv)

thus,

total time taken= 1+0.5+0.3+0.25 (from i,ii,iii,iv)

=2.05 hrs

average speed = total distance /total time

=40/2.05

=19.5 km/hr