A train runs of 2 hrs at the speed of 40 km/h and then runs for `4(1)/(2)` hrs at the speed of 60 km/h and then the runs for `3(1)/(2)` hrs, at the speed of 70 km per hour. Find the average speed of the train.

Options

A. 59.5 km/h
B. 80 km/h
C. 56.87 km/h
D. 57.1 km/h

Answer

A

Explanation

`"Average speed"`
`=("Total Distance Covered")/("Total Time Taken")`
Total distance covered
`=(2xx40)+((9)/(2)xx60)+((7)/(2)xx70)km`
`=(80+270+245)km`
`=595km`
Total time taken
`=2+(9)/(2)+(7)/(2)`
`=(4+9+7)/(2)=(20)/(2)="10 hours"`
`therefore" Average speed "=(595)/(10)`
`=59.5km" per hour"`