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A train crosses a person in 15 seconds and a bridge of 120 meters in 4

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Bunuel
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A train crosses a person in 15 seconds and a bridge of 120 meters in 4 [#permalink] A train crosses a person in 15 seconds and a bridge of 120 meters in 4   28 Jan 2019, 04:20
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A train crosses a person in 15 seconds and a bridge of 120 meters in 40 seconds. What is the length of the train?

A. 100m

B. 85m

C. 75m

D. 72m

E. 70m
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Archit3110
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Re: A train crosses a person in 15 seconds and a bridge of 120 meters in 4 [#permalink] A train crosses a person in 15 seconds and a bridge of 120 meters in 4   28 Jan 2019, 06:15
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Bunuel
A train crosses a person in 15 seconds and a bridge of 120 meters in 40 seconds. What is the length of the train?

A. 100m

B. 85m

C. 75m

D. 72m

E. 70m


let length of train be x
so
speed of man crossing x/15
and bridge ; x+120/40
x/15 = x+120/40
solve for x
we get 72 m
IMO D
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Ish1996
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Re: A train crosses a person in 15 seconds and a bridge of 120 meters in 4 [#permalink] A train crosses a person in 15 seconds and a bridge of 120 meters in 4   04 Mar 2019, 07:35
Archit3110
Bunuel
A train crosses a person in 15 seconds and a bridge of 120 meters in 40 seconds. What is the length of the train?

A. 100m

B. 85m

C. 75m

D. 72m

E. 70m


let length of train be x
so
speed of man crossing x/15
and bridge ; x+120/40
x/15 = x+120/40
solve for x
we get 72 m
IMO D

How come you assumed that the speeds at which the train crossed the man and the bridge are equal?
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Archit3110
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Posts: 8077
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545 Q79 V79 DI73
GPA: 4
WE:Marketing (Energy)
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Re: A train crosses a person in 15 seconds and a bridge of 120 meters in 4 [#permalink] A train crosses a person in 15 seconds and a bridge of 120 meters in 4   04 Mar 2019, 10:01
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Ish1996
unless not given specifically in question that there is an increase in speed of train after it crosses man, we cannot consider any increase in speed of train ,hence the speed of train is considered the same while solving the question.
Hope this helps.

Ish1996
Archit3110
Bunuel
A train crosses a person in 15 seconds and a bridge of 120 meters in 40 seconds. What is the length of the train?

A. 100m

B. 85m

C. 75m

D. 72m

E. 70m


let length of train be x
so
speed of man crossing x/15
and bridge ; x+120/40
x/15 = x+120/40
solve for x
we get 72 m
IMO D

How come you assumed that the speeds at which the train crossed the man and the bridge are equal?
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bumpbot
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Re: A train crosses a person in 15 seconds and a bridge of 120 meters in 4 [#permalink] A train crosses a person in 15 seconds and a bridge of 120 meters in 4   07 Jul 2024, 14:54
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: A train crosses a person in 15 seconds and a bridge of 120 meters in 4 [#permalink]
07 Jul 2024, 14:54
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