Question

12. A train travels at 60 km/h for 1 hour. Its then travels at a speed of 70 km/h for the next 1 hours.
Find the average speed of the train.
[​

Answer 1

Question-

A train travels at 60 km/h for 1 hour. Its then travels at a speed of 70 km/h for the next 1 hours.

Find the average speed of the train.

Answer-

We need to find the average speed of the train.

Let us consider the first case,

The train travels at a speed of 60 km/h for a time of 0.52 h

We know that Speed = distance / time = 30km/hr

Hence Distance = Speed X Time

Distance=60 x 0.52 = 31.2 km ————–(i)

Now, in the second case, the train travels at a speed of 30 km/h for a time of 0.24 hr.

We know that speed = distance / time = 30 km/hr

Distance = Speed X Time

Distance=30 × 0.24 = 7.2 km ———–(ii)

Here in the third case, the train travels at a speed of 70km/h for a time of 0.71 hr.

We know thatspeed = distance / time = 70km/hr

Hence Distance = Speed X Time

=70 × 0.71 hr .

speed = distance / time = 70km/hr

Distance = 70 × 0.71 = 49.7 km ———–(iii)

Combining all the equations (i), (ii) and (iii) and adding we get,

Total distance travelled

= (31.2 + 7.2 + 49.7) km = 88.1 km .

Total time taken = (0.52 + 0.24 + 0.71) hr = 1.47 hr .

Average speed = Total distance travelled / Total time taken

= (88.1/1.47) km /hr

Hence, average speed = 59.9 km/hr

Hope it helps you!!