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If the ratio of the number of teachers to the number of

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gtr022001
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If the ratio of the number of teachers to the number of [#permalink] New post   Updated on: 31 Mar 2014, 11:55
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If the ratio of the number of teachers to the number of students is the same in School District M and School District P, what is the ratio of the number of students in School District M to the number of students in School District P ?

(1) There are 10,000 more students in School District M than there are in School District P.
(2) The ratio of the number of teachers to the number of students in School District M is 1 to 20.

OPEN DISCUSSION OF THIS QUESTION IS HERE: if-the-ratio-of-the-number-of-teachers-to-the-number-of-143680.html
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E

Originally posted by gtr022001 on 21 May 2011, 11:12.
Last edited by Bunuel on 31 Mar 2014, 11:55, edited 2 times in total.
Edited the question.
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gtr022001
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Re: og12: School District M and School District P [#permalink] New post   21 May 2011, 11:49
jamifahad wrote:
is OA E?


kindly explain why E? :)
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Re: og12: School District M and School District P [#permalink] New post   24 May 2011, 00:17
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a. Teachers : Students = Tm:Sm. and Tp:Sp. Sm:Sp = ? (asked)

now, Sm-Sp = 1000 means Sm: (1000-Sm) = not known, Hence not sufficient.

b Tm:Sm = Tp:Sp = 1:20 gives nothing for Sm:Sp. Not sufficient.

a+b Tm:Sm = 1/20 Tp:(1000-Sm) = 1/20 gives not relative information between Tp Tm and Sm.Hence Not sufficient.

Thus E.
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Re: og12: School District M and School District P [#permalink] New post   24 May 2011, 19:30
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T1/S1 = T2/S2

S1/S2 = ?

(1)

S1 = S2 + 1000

Not sufficient

(2)


T1/S1 = 1/20

Not sufficient

(1) + (2) Not sufficient

Answer - E
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Re: og12: School District M and School District P [#permalink] New post   24 May 2011, 19:51
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sm/sp =?

1. Not sufficient

as we dont know sp.


sm = 10000 + sp
=> sm/sp = 10000/sp +1

2. Not sufficient

tm/sm = 1/20 = tp/sp

not enough to find out sm/sp.

Together,

still not sufficient.

Answer is E.
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Re: og12: School District M and School District P [#permalink] New post   28 May 2011, 09:45
OA is E - this was a DS in the Original Guide 12th edition.
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Re: If the ratio of the number of teachers to the number of [#permalink] New post   31 Mar 2014, 11:40
gtr022001 wrote:
If the ratio of the number of teachers to the number of students is the same in School District M and School District P, what is the ratio of the number of students in School District M to the number of students in School District P ?

(1) There are 10,000 more students in School District M than there are in School District P.
(2) The ratio of the number of teachers to the number of students in School District M is 1 to 20.

Official Guide 12 Question

GMAT Official Guide 12

Question: 58
Page: 277
Difficulty: 600

Find All Official Guide Questions

Video Explanations:



Hi ,
If Tm:Sm = Tp:Sp = 1/20
so Applying Alternendo
Tm:Tp= Sm:Sp = 1/20
So isnt 2 Sufficient?
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Re: If the ratio of the number of teachers to the number of [#permalink] New post   31 Mar 2014, 11:53
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abid1986 wrote:
gtr022001 wrote:
If the ratio of the number of teachers to the number of students is the same in School District M and School District P, what is the ratio of the number of students in School District M to the number of students in School District P ?

(1) There are 10,000 more students in School District M than there are in School District P.
(2) The ratio of the number of teachers to the number of students in School District M is 1 to 20.

Official Guide 12 Question

GMAT Official Guide 12

Question: 58
Page: 277
Difficulty: 600

Find All Official Guide Questions

Video Explanations:



Hi ,
If Tm:Sm = Tp:Sp = 1/20
so Applying Alternendo
Tm:Tp= Sm:Sp = 1/20
So isnt 2 Sufficient?


Yes, from \(\frac{T_m}{S_m}=\frac{T_p}{S_p}\) we can get that \(\frac{S_m}{S_p}=\frac{T_m}{T_p}\) but it does NOT mean that the ratio will remain the same, so it does not mean that since \(\frac{T_m}{S_m}=\frac{1}{20}\), then \(\frac{S_m}{S_p}=\frac{T_m}{T_p}\) will also be 1/20. Play with some numbers to prove that.

If the ratio of the number of teachers to the number of students is the same in School District M and School District P, what is the ratio of the number of students in School District M to the number of students in School District P ?

Given that \(\frac{T_m}{S_m}=\frac{T_p}{S_p}\), where \(T_m\) and \(S_m\) are the numbers of teachers and students, respectively, in District M, and \(T_p\) and \(S_p\) are the numbers of teachers and students, respectively, in District P.

We need to find the value of \(\frac{S_m}{S_p}\) --> \(\frac{S_m}{S_p}=\frac{T_m}{T_p}\)

(1) There are 10,000 more students in School District M than there are in School District P --> \(S_m=S_p+10,000\). Not sufficient.

(2) The ratio of the number of teachers to the number of students in School District M is 1 to 20 --> \(\frac{T_m}{S_m}=\frac{1}{20}\). Not sufficient.

(1)+(2) Still not sufficient, consider \(S_p=1,000\) and \(S_m=11,000\) (answer 11) AND \(S_p=10,000\) and \(S_m=20,000\) (answer 2).

Answer: E.

All OG13 questions are here: the-official-guide-quantitative-question-directory-143450.html

OPEN DISCUSSION OF THIS QUESTION IS HERE: if-the-ratio-of-the-number-of-teachers-to-the-number-of-143680.html
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Re: If the ratio of the number of teachers to the number of [#permalink]
31 Mar 2014, 11:53
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