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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] New post   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] New post   28 Jan 2019, 06:15
Bunuel wrote:
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] New post   04 Mar 2019, 07:35
Archit3110 wrote:
Bunuel wrote:
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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Re: A train crosses a person in 15 seconds and a bridge of 120 meters in 4 [#permalink] New post   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 wrote:
Archit3110 wrote:
Bunuel wrote:
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?
GMAT Club Bot
gmatclubot
Re: A train crosses a person in 15 seconds and a bridge of 120 meters in 4 [#permalink]
04 Mar 2019, 10:01
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