A train travels 20 km at uniform speed of 60 km h -1 and uniform and the next 20 km at the uniform speed 80 kilometre as -1 calculate the average speed
Answers
Answer:
the distance covered by the train is 40 km.
at 1st 20 km the speed of train was 60 km/HR
time ( T1) = 20/60 h = 1/ 3 h
next 20 km at the speed of 80 km/ HR
time (t2) = 20 /80h = 1/4h
avg.speed = total distance covered/ total time taken
= 40(1/3+1/4)
=40{(3+4)/12}
=40*12/7 = 68.57km/HR..
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Given that, a train travels 20 km at a uniform speed of 60 km/hr and the next 20 km at the uniform speed of 80 km/hr.
We have to find the average speed of the train.
Distance = Speed × Time
Case 1)
"Train travels 20 km at a uniform speed of 60 km/hr."
Distance = 20 km & speed = 60 km/hr
→ d1 = s1 × t1
→ 20 = 60 × t1
→ 1/3 = t1 ...............(1st equation)
Case 2)
"Train travels 20 km at a uniform speed of 80 km/hr."
Distance = 20 km & speed = 60 km/hr
→ d2 = s2 × t2
→ 20 = 80 × t2
→ 1/4 = t2 ...............(2nd equation)
Now,
Average speed is defined as the ratio of total distance covered by the total time taken.
Total distance covered = (20 + 20)km = 40 km
Total time taken = t1 + t2
= 1/3 + 1/4
= (4 + 3)/12
= 7/12
Average speed = (Total distance covered)/(Total time taken)
= 40/(7/12)
= (40*12)/7
= 68.57
= 69 (approx.)
Therefore, the average speed of the train is 69 km/hr.