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- A train moves past a telegraph post and a bridge 264 m long in 8 seconds and 20 seconds respectively.
Question 1:
A train moves past a telegraph post and a bridge 264 m long in 8 seconds and 20 seconds respectively.What is the speed of the train?
A. 69.2 km/hr
B. 70 km/hr
C. 79 km/hr
D. 79.2 km/hr
Feedback Let the length of the train be x metres and its speed by y m/sec.
Time = Length / Speed of the train
Given,A train moves past a telegraph post in 8 seconds.
Then, x/y = 8
=> x = 8y
Now, the same train moves past a bridge of 264 m long in 20 seconds.
=> (x + 264) / y = 20
Subs x = 8y in the above eqn, we get=> (8y + 264) = 20y=> 20y - 8y = 264
=> 12y = 264
=> y = 22.
Therefore Speed = 22 m/sec = ( 22 x 18 /5) km/hr = 79.2 km/hr.
Time = Length / Speed of the train
Given,A train moves past a telegraph post in 8 seconds.
Then, x/y = 8
=> x = 8y
Now, the same train moves past a bridge of 264 m long in 20 seconds.
=> (x + 264) / y = 20
Subs x = 8y in the above eqn, we get=> (8y + 264) = 20y=> 20y - 8y = 264
=> 12y = 264
=> y = 22.
Therefore Speed = 22 m/sec = ( 22 x 18 /5) km/hr = 79.2 km/hr.
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