A train travels with a speed of 30 km/h for 30 min and then with of speed of 60 km/h for one hour. Find (a) the total distance travelled by the train, (b) the total time of travel and (c) the average speed in km/h
Answers
Answer:
Speed of car for first 30 minutes = 30 km h^{-1}h
−1
Speed of car for next 1 hour = 40 km h^{-1}h
−1
(a) total distance travelled by the car
First case
Speed = distance / time
distance = speed x time
= 30 x 0.5 ---- (30 min = 0.5 hour)
= 15 km ---- (i)
Second case
speed = 40 km h^{-1}h
−1
distance = 40 km x 1
= 40 km ---- (ii)
Adding (i) and (ii)
Total distance = 15 km + 40 km
= 55 km
(b) total time of travel = 0.5 hr + 1.0 hr = 1.5 hr
(c) average speed = total distance travelled/total time taken
= 5.5 km/ 1.5 hr
= 36.67 km h^{-1}h
−1
Answer:
Given:-
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.
Solution :-
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