21. A train covers first 200 km of its ioey at 70 km/hr. Due to bad Weather a train covers the next 200 a km of its journey at 60 km/hr.. What will be the average speed for the first 400 km of its journey? O 78.6 km/hr O 67.6 km/hr O 76.6 km/hr O 64.6 km/hr
Answers 2
Step-by-step explanation:
First let us find the time taken for the first 50 kms(t1)
t1 = distance/speed
t1 = 50/40
t1 = 5/4 hrs.
now let us find the time taken for the whole journey(T)
T = d/s
T = 200/60
T = 20/6
T = 10/3
now let us find the leftover time(t2)
t2 = T - t1
t2 = 10/3 - 5/4 (LCM is 12)
t2 = (40-15)/12
t2 = 25/12
now with the time and distance let us find the speed.
S = d/t
S = 150/25/12
S = 150 x 12/25( 25 x 6 =150)
S = 6 x 12
S = 72km/hr
checking
average speed = total distance/total time
Avg. Speed = 200/10/3
Avg. speed = 200 x 3/10
Avg. speed = 20 x 3
Avg. speed = 60km/hr.
Answer = 72km/hr
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Author:
sofíawalton
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Concept:
Speed is determined by dividing the distance travelled by the time taken to travel it. It gives the amount of time it took to travel a certain distance divided by the distance travelled.
Speed is inversely correlated with time and directly correlated with distance.
As a result, distance equals speed x time, and time equals distance divided by speed; as speed rises, distance travelled will shorten, and vice versa
Speed = distance/ time.
Given:
train covers first 200 km of its ioey at 70 km/hr. Due to bad Weather a train covers the next 200 a km of its journey at 60 km/hr
Find:
What will be the average speed for the first 400 km of its journey?
Solution:
Since the distances are equal
we can write,
avg speed =2v₁ v₂/(v₁ +v₂)
=2 x70 x 60/130
=64.6km/hr
Therefore, the average speed =64.6km/hr
#SPJ2
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Author:
mollyl34c
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