Question

A truck travels to a place 120 km away at an speed of 40 km/h and returns with a speed of 30 km/h. Find the average speed of the truck for the whole journey?

1. \(34 \frac 2 7\) km/h
2. \(28 \frac 2 7\) km/h
3. \(38 \frac 2 7\) km/h
4. \(40 \frac 2 7\) km/h

Answer 1

Correct Answer - Option 1 : \(34 \frac 2 7\) km/h

Given:

Distance traveled in one side = 120 km

Speed while going = 40 km/h

Speed while returning = 30 km/h

Formula used:

Average speed = Total distance travelled/Total time taken

Calculation:

Time taken while going = (120/40) hr

= 3 hrs

Time taken while returning = (120/30) hr

= 4 hr

Total distance travelled while going and returning = (120 × 2) km

= 240 km

∴ Average speed of the truck = (240/7) km/h

= \(34 \frac 2 7\) km/h