Question

A man works on a striaght road from his home to market 2.5km away dwith a speed of 5km/h.Finding the market closed, he instantly truns and walk back home with a speed of 7.5km/h. The average speed of the man over the interval of time 0.40min.Is equal to?

Answer 1

5.625km/h

Step-by-step explanation:

We are given that

Distance between home and market, d=2.5 km

Speed, v1=5km/h

Speed, v2=7.5 km/h

We have to find the average speed of the man over the interval of time 0 to 40min.

Time,
`t=(distance)/(speed)`

Using the formula

`t_1=(2.5)/(5)=0.5 h=0.5* 60=30 min`

1 hour =60 min

`t_2=(2.5)/(7.5)=(1)/(3)hour=(60)/(3)=20min`

Distance traveled by man in 10 min with speed 7.5 km/h=
`(2.5)/(20)* 10=2.5/2km`

Therefore,

Total distance covered=2.5+2.5/2=3.75 km

Time=40 min=40/60=2/3 hour

Average speed=
`(total\;distance)/(total\;time)`

Average speed=
`(3.75)/(2/3)=5.625km/h`