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# Here's another one I picked off the Beginners forum. It's a

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GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5068
Location: Singapore
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Here's another one I picked off the Beginners forum. It's a [#permalink]  23 Jun 2005, 00:25
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Here's another one I picked off the Beginners forum. It's a straight-forward question, but apart from deriving the answer by brute-force, I want to see if anyone has a more systematic approach.

Trains leave a town B at 3pm and every 10 hours after that. train leave town C at 4pm and every 15 hours after that. if trains follow this schedule beginning on a monday, what is the earliest day on which the trains leave at the same time?
Director
Joined: 13 Nov 2003
Posts: 790
Location: BULGARIA
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it seems to me that they will never leave at the same time.Every 30 hours the cycle will repeat and the trains will leave with one hour gap.
Director
Joined: 27 Dec 2004
Posts: 908
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1pm the following monday. they should both leave at the same time
Manager
Joined: 27 Jan 2005
Posts: 100
Location: San Jose,USA- India
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Kudos [?]: 1 [0], given: 0

15x-10y=1
none of x and y will solve it.So will never meet.
Intern
Joined: 10 Jun 2005
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Kudos [?]: 0 [0], given: 0

I think they wont start at same time as a cycle of 30 hrs is there LCM of 30 and 24(one day) is 120 ie after every 120 hrs ie ( from 150th hour) they will start from thier respective times.
Intern
Joined: 10 Jun 2005
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700Plus wrote:
15x-10y=1
none of x and y will solve it.So will never meet.

And what will be answer if suppose the second train started at 8pm instead of 4 pm ?

Thanks
GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5068
Location: Singapore
Followers: 23

Kudos [?]: 194 [0], given: 0

I went the brute-force way:

Train B
1500, Mon
0100, Tue
1100, Tue
2100, Tue
0700, Wed
1700, Wed
0300, Thu
1300, Thu
2300, Thu
0900, Fri
1900, Fri
0500, Sat
etc

Train C
1600, Mon
0700, Tue
2200, Tue
1300, Wed
0400, Thu
1900, Thu
1000, Fri
0100,
etc

Not very elegant, as you can see, although I arrived at the same answer: The trains will never meet.
Senior Manager
Joined: 30 May 2005
Posts: 277
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Kudos [?]: 11 [0], given: 0

700Plus wrote:
15x-10y=1
none of x and y will solve it.So will never meet.

700Plus"
PLZ can you explain how you come to this equation
what x and y stands for why do you substract nd equate to 1

THANKS
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