Answer:
5.625km/h
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,[tex]t=\frac{distance}{speed}[/tex]
Using the formula
[tex]t_1=\frac{2.5}{5}=0.5 h=0.5\times 60=30 min[/tex]
1 hour =60 min
[tex]t_2=\frac{2.5}{7.5}=\frac{1}{3}hour=\frac{60}{3}=20min[/tex]
Distance traveled by man in 10 min with speed 7.5 km/h=[tex]\frac{2.5}{20}\times 10=2.5/2km[/tex]
Therefore,
Total distance covered=2.5+2.5/2=3.75 km
Time=40 min=40/60=2/3 hour
Average speed=[tex]\frac{total\;distance}{total\;time}[/tex]
Average speed=[tex]\frac{3.75}{2/3}=5.625km/h[/tex]
