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QR DS 63: A Town T has 20,000 residents, 60 percent of whom

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QR DS 63: A Town T has 20,000 residents, 60 percent of whom [#permalink]  21 Feb 2011, 06:06
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QR DS 63: A Town T has 20,000 residents, 60 percent of whom are female. What percent of the residents were born in Town T?

(1) The number of female residents who were born in Town T is twice the number of male residents who were not born in Town T.
(2) The number of female residents who were not born n Town T is twice the number of female residents who were born in Town T.
[Reveal] Spoiler: OA

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Re: QR DS 63 [#permalink]  21 Feb 2011, 06:20
A Town T has 20,000 residents, 60 percent of whom are female. What percent of the residents were born in Town T?

This question can be best described using a table. I don't know how would I draw that. Someone please suggest.

Female=12000
Male=8000

Female born in T=x
Female not born in T=12000-x

Male born in T=y
Male not born in T= 8000-y

(1) The number of female residents who were born in Town T is twice the number of male residents who were not born in Town T.
x=2*y
Not sufficient.

(2) The number of female residents who were not born n Town T is twice the number of female residents who were born in Town T.
12000-x=2x
3x = 12000
x=4000
We know the number of female born in T; 4000; Number of females not born; 8000
Know nothing about the male born in T i.e. y.

Combining both;
x=2y
4000 = 2y
y=2000

Total people born in T=2000+4000=6000 or (6/20)*100=30%
Sufficient.

Ans: "C"
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Re: QR DS 63 [#permalink]  21 Feb 2011, 07:10
it will be x = 2*(8000-y) but that doesn't change the answer.
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A complicated Math, which has not been discussed. [#permalink]  14 Aug 2011, 05:01
A Town T has 20,000 residents, 60 percent of whom are female. What percent of the residents were born in Town T?

(1) The number of female residents who were born in Town T is twice the number of male residents who were not born in Town T.

(2) The number of female residents who were not born n Town T is twice the number of female residents who were born in Town T.
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Re: A complicated Math, which has not been discussed. [#permalink]  14 Aug 2011, 08:50
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It should be 3 equations to 3 unknowns, C sufficient.

For some reason I can't seem to find the answers though, maybe some number is wrong?

EDIT: couldn't get it right, got frustrated, searched the net. The original version of the problem seems to be:

(1) The number of female residents who were born in Town T is twice the number of male residents who were not born in Town T.

(2) The number of female residents who were not born in Town T is twice the number of female residents who were born in Town T.

Also: qr-ds-109774.html
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Re: A complicated Math, which has not been discussed. [#permalink]  16 Aug 2011, 07:00
the question seems to be incorrect..
in the final equation, i get total male as 6000 whereas the question gives 8000..
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Re: A complicated Math, which has not been discussed. [#permalink]  16 Aug 2011, 13:04
I guess some issue in the question. C should be the answer, but not able to solve the equations.
Then E is the answer as we are not able to solve.
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Re: A complicated Math, which has not been discussed. [#permalink]  17 Aug 2011, 10:30
jansam123 wrote:
I guess some issue in the question. C should be the answer, but not able to solve the equations.
Then E is the answer as we are not able to solve.

Born = B
Not Born = N
Female = F
Male = M
Total = T

After Statement -1

F M T
B 2x - -
N - x ?
T 12 8 20

Can't calculate NT, NOT Sufficient

After Statement -2

F M T
B 2x - -
N 4x - ?
T 12 8 20

Can't calculate NT, NOT Sufficient

Combining both, can calculate for x = 5

F M T
B 2x - -
N 4x x ?
T 12 8 20

=>

F M T
B 4 - -
N 8 2 10
T 12 8 20

So both together are Sufficient
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Re: QR DS 63 [#permalink]  17 Aug 2011, 10:31
Sorry, I tried to make it more understandable but it seems formatting doesn't work
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Re: QR DS 63 [#permalink]  18 Aug 2011, 10:29
let's make a table and write all values from stem, statement 1 & 2

From Stem, total females = 60% of 20,000 = 12,000
From statement 1, if male(M) not born (NB) in town T are x, then female(F) born(B) in town = 2x
From statement 2, F(NB) = 2 F(B)
Combining both the statements, we have following table

| M | F |
-------|-------|------- |---------
B | | 2x |
-------|-------|------- |--------
NB | x | 2(2x) |
-------|-------|--------|------------
| | 12000 |

So, 2x + 2(2x) = 12,000.

Rest is all arithmetic, we can calculate each cell, hence final answer. Remember no need to go fro exact answer. We now know, both statements are sufficient. Answer is C.
Re: QR DS 63   [#permalink] 18 Aug 2011, 10:29
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