Math, asked by guddashanu5789, 1 year ago

A train passes two bridges of length 800 m and 400 m in 100 seconds and 60 seconds respectively. The length of the train is?
A) 200 m
B) 90 m
C) 120 m
D) 150 m

Answers

Answered by Anonymous
14

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Step-by-step explanation:

Let the length of the train be x m .

The train passes the bridge of length 800 m in 100 s .

The train passes the bridge of 400 m in 60 s .

The speed of the train will be same while travelling through both the bridges .

Speed = distance / time .

First case

Distance will be 800 m + x m

⇒ Distance = ( 800 + x ) m

Time given to us is 100 s .

Speed = distance/time

⇒ Speed = ( 800 + x )/100 m/s ------(1)

Second case

Distance will be 400 m + x m

⇒ Distance = ( 400 + x ) m

Time given to us is 60 s .

Speed = distance/time

⇒ Speed = ( 400 + x )/60 m/s -----(2)

From (1) and (2) speed will remain constant :

( 800 + x ) / 100 m/s = ( 400 + x ) / 60 m/s

⇒ ( 800 + x ) / 5 = ( 400 + x ) / 3

⇒ 3 ( 800 + x ) = 5 ( 400 + x )

⇒ 2400 + 3 x = 2000 + 5 x

⇒ 5 x - 3 x = 2400 - 2000

⇒ 2 x = 400

⇒ x = 400 / 2

⇒ x = 200

The length of the train is 200 m .

Answered by StylishhhhGirl
5
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Option A

____________________________________

Let length of the train be x m and speed of the train is s kmph.

Speed, s = (x+800)/100 .... (i)

Speed, s = (x+400)/60 .... (ii)

Equating equation (i) and (ii), we get,

✏ (x+800)/100 = (x+400)/60

✏ 5x+200 = 3x+2400;

✏ 2x = 400;

✏ x = 200 m.
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