A train travels at a speed of 60km/h for 0.52h, of 30km/h for the next 0.24h and then at 70km/h for the next 0.71h. What is the average speed of the train?
Answers
Given that :A train travels at a speed of 60km/h for 0.52h, of 30km/h for the next 0.24h, and then at 70km/h for the next 0.71h.
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
Answer:
(i) In the first case, the train travels at a speed of 60 km/h for a time of 0.52 h
Now, Speed = distance / time = 30km/hr
Distance = 60 x 0.52 = 31.2 km --- i)
(ii) In the second case, the train travels at a speed of 30 km/h for a time of 0.24 hr.
Now, speed = distance / time = 30 km/hr
Distance = 30 × 0.24 = 7.2 km --- ii)
(iii) In the third case, the train travels at a speed of 70km/h for a time of 0.71 hr.
Now, speed = distance / time = 70km/hr
Distance = 70 × 0.71 hr .
Now speed = distance / time = 70km/hr
Distance = 70 × 0.71 = 49.7 km ---iii)
From equation 1,2 & 3 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
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