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# Ratio PS

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Current Student
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Joined: 20 Jul 2009
Posts: 185
Location: Africa/Europe
Schools: Kellogg; Ross (\$\$); Tuck

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24 Jul 2009, 13:36
1
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During a certain month, Dave watched n-2hours movies and p 90-minutes movies. Had he spent the same amount of time watching TV, he could have watched 60 thirty minutes TV shows.
Each of the following is a possible ratio of n to p except:

3:16
1:2
2:3
9:8
3:1

could not find an easy way to solve it.

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

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

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Manager
Joined: 18 Jul 2009
Posts: 166
Location: India
Schools: South Asian B-schools

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24 Jul 2009, 15:09
i got my ans by sustitution method.....if u have followed the same then sorry ....

120n+90p = 60x30

4n+3p = 60

then substituting....
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Bhushan S.
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Senior Manager
Joined: 18 Jun 2009
Posts: 349
Location: San Francisco

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24 Jul 2009, 16:16
Same here

I got 4n + 3p = 60

and then worked back with the answers and found A is the answer
Current Student
Affiliations: ?
Joined: 20 Jul 2009
Posts: 185
Location: Africa/Europe
Schools: Kellogg; Ross (\$\$); Tuck

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25 Jul 2009, 00:51
gmanjesh wrote:
Same here

I got 4n + 3p = 60

and then worked back with the answers and found A is the answer

humm...
how do you substituate? because if n is 3 and p is 16 we will have 4n+3p=12+48=60
Manager
Joined: 18 Jul 2009
Posts: 166
Location: India
Schools: South Asian B-schools

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25 Jul 2009, 12:06
gmanjesh wrote:
Same here

I got 4n + 3p = 60

and then worked back with the answers and found A is the answer

humm...
how do you substituate? because if n is 3 and p is 16 we will have 4n+3p=12+48=60

OK here we know 3:16 as option (1) assume common factor as 1 for 1st iterration hence put 3 & 16 then check it fits in (4x3+16x3 = 60)...now if this is not true..then for second iterration take 6 & 32 then check.....
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Bhushan S.
If you like my post....Consider it for Kudos

Senior Manager
Joined: 25 Jun 2009
Posts: 286

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25 Jul 2009, 12:43
By the way, AO is C

Whats the source of this question?

And if we substitute then A and D both satisfies ..It seems the question or may be the answer choice is wrong.

Cheers
Manager
Joined: 03 Jul 2009
Posts: 103
Location: Brazil

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25 Jul 2009, 13:45
3
There is a simple and fast way to resolve this question:

First of all you start with the equation that everybody has suggested:

120n + 90p = 60*30
4n + 3p = 60

Now here is the key.

You need only to worry about the first part of the equation "4n + 3p".

You substitute the values of n and p and check if the result is A FACTOR OF 60. If it is, then it is a possible solution, because you know that you need only to multiply the equations by a factor to get 60 as a result.

Step by step:

A 3:16 --> 4*3 + 3*16 = 60 - ok here we are lucky. This is a solution.
B 1:2 --> 4*1 + 3*2 = 10 This is another solution because 10 is a factor of 60. If we multiply the numbers of the ration by 6, we will have 6:12, and the result will be 4*6 + 3*12 = 60. But we don't need to multiply to see that the result will be 60. When we see 12, we think: It is enough!
C 2:3 --> 4*2 + 3*3 = 17 CORRECT. Here is our solution. There is no number to multiply to get a result of 60, therefore it is impossible to have the ratio 2:3
D 9:8 --> 4*9 + 3*8 = 60 lucky again
E 3:1 --> 4*3 + 3*1 = 15. It is a possible solution.

Notice that explaining this in detail might be look time consuming, but try to do this question, following this reasoning, ans you will see it is very fast.

Goos studies.

PS.: If you've appreciated the explanation, consider a kudo. I want to access those GMATClub tests!!!
Senior Manager
Joined: 25 Jun 2009
Posts: 286

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25 Jul 2009, 14:00
nitishmahajan wrote:
By the way, AO is C

Whats the source of this question?

And if we substitute then A and D both satisfies ..It seems the question or may be the answer choice is wrong.

Cheers

My bad I misread the question .. I didnt see the except in the end !..
Current Student
Affiliations: ?
Joined: 20 Jul 2009
Posts: 185
Location: Africa/Europe
Schools: Kellogg; Ross (\$\$); Tuck

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25 Jul 2009, 14:15
nitishmahajan wrote:
By the way, AO is C

Whats the source of this question?

And if we substitute then A and D both satisfies ..It seems the question or may be the answer choice is wrong.

Cheers

I had this question from princeton review. I attached a file here with the original question.

Attachment:

gmatQ.JPG [ 36.04 KiB | Viewed 1148 times ]
Senior Manager
Joined: 25 Jun 2009
Posts: 286

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25 Jul 2009, 14:28
nitishmahajan wrote:
By the way, AO is C

Whats the source of this question?

And if we substitute then A and D both satisfies ..It seems the question or may be the answer choice is wrong.

Cheers

I had this question from princeton review. I attached a file here with the original question.

Attachment:
gmatQ.JPG

Thanks, I got it I didnt read the EXCEPT in the first post; thats why got confused my bad !
Director
Joined: 01 Apr 2008
Posts: 827
Name: Ronak Amin
Schools: IIM Lucknow (IPMX) - Class of 2014

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26 Jul 2009, 07:09
excellent question...+1 for the solution and +1 for the question.
I discovered a new pattern
Manager
Joined: 03 Jul 2009
Posts: 103
Location: Brazil

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27 Jul 2009, 06:33
Thank you guys!!!
Director
Joined: 05 Jun 2009
Posts: 680
WE 1: 7years (Financial Services - Consultant, BA)

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27 Jul 2009, 07:17
Nice explanation!
+1

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Re: Ratio PS &nbs [#permalink] 27 Jul 2009, 07:17
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# Ratio PS

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