For a man who walks 72 m at a uniform speed of `2 m//s`, then runs at a uniform speed of `4 m//s` for 5 minute and then again walks at a speed of `1 m//s` for 3 minutes. His average speed is

Explanation

Where `s_(1)=720m and t_(1)=(s_(1))/(v_(1))=360s=6 min`.
`s_(2)=(4)(5)(60)=1200m, t_(2)=300s`
`s_(3)=(1)(3)(60)=180m, t_(3)=180s`
`v_(avg)=(s_(1)+s_(2)+s_(3))/(t_(1)+t_(2)+t_(3))=(720+1200+180)/(360+300+180)`
`implies v_(avg)=2.5 m//s`