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Circular gears P and Q start

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Director
Joined: 27 Jun 2008
Posts: 526
WE 1: Investment Banking - 6yrs
Circular gears P and Q start [#permalink]

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08 Dec 2008, 13:13

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Manager
Joined: 14 Jun 2007
Posts: 158
Location: Vienna, Austria
Re: GMAT Prep - 2 questions [#permalink]

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08 Dec 2008, 13:21
for the first one:
7-t48928?hilit=circular+gear

OA is D
Manager
Joined: 23 Nov 2008
Posts: 79
Re: GMAT Prep - 2 questions [#permalink]

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09 Dec 2008, 17:27
2
KUDOS
1 D and 2 B

1) 10 revolutions in a minute = 1 rev per 1/10 minute = x revs per x/10 mins
40 revs /minute = 1 revs per 1/40 minutes = x+6 revs per (x+6)/40 mins

x/10 = (6+x)/40
x= 2

time= 2/10 of a minute = 12 seconds

2) isosceles right triangle has sides in the ratio x:x:xv2
2x+xv2 = 16 + 16v2
x(2+v2) = 16 + 16v2
x= 16(1+v2)/v2(v2+1) = 16/v2 = 8.2/v2 = 8v2
hypotenuse=xv2 = 8v2.v2=16
Senior Manager
Joined: 30 Nov 2008
Posts: 482
Schools: Fuqua
Re: GMAT Prep - 2 questions [#permalink]

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10 Dec 2008, 09:36
Even I go with 1 - D and 2 - B.

For 1 Q, here is my solution.

P takes 10 Rev per Min ==> 10 Rev - 60 Sec ==> 1 Rev = 6 Sec
Q takes 40 Rev per Min ==> 40 Rev - 60 Sec ==> 1 Rev = 3/2 Sec.

Let x be the number of revolution taken by P and x+6 be the Rev taken by Q. TIt is said that for P taking x revolutions is same as Q taking X + 6 revolutions.

P takes 6x sec and Q takes (x+6)3/2 Sec.

6x= (x +6) 3/2. ==> 12x = 3x + 18 ==> x = 2.

Substitting x in either of the eq, we get time as 12 sec.

Question 2, same solution as twilight provided.

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

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Re: GMAT Prep - 2 questions   [#permalink] 10 Dec 2008, 09:36
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Circular gears P and Q start

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