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#1 2014-07-20 20:06:12

burgess
Member
Registered: 2014-06-26
Posts: 49
Website

problem on trains

Need help to solve math homework problem

A train overtakes two persons walking in the same direction in which the train is going, at the rate of 2 kmph and 4 kmph and passes them completely in 9 and 10  seconds respectively. Then what is the length of the train?

Thanks

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#2 2014-07-21 01:57:44

bobbym
bumpkin
From: Bumpkinland
Registered: 2009-04-12
Posts: 109,606

Re: problem on trains

Hi;


In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

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#3 2014-07-25 21:48:12

Nehushtan
Member
Registered: 2013-03-09
Posts: 957

Re: problem on trains

Let the length of the train (in km) be
.

Let the speed (in kph) of the train relative to the first person be
; then its speed relative to the second person is
.

Therefore:

Hence:

So the train’s length is 0.05 km – i.e. 50 m.


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#4 2014-08-26 21:56:06

burgess
Member
Registered: 2014-06-26
Posts: 49
Website

Re: problem on trains

Thanks for your replies

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#5 2014-09-15 23:51:58

GreatSandy
Member
Registered: 2014-09-15
Posts: 15

Re: problem on trains

the train’s length is 5000 cm

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