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Lake A has a duck population of 30 females and 36 males.

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Lake A has a duck population of 30 females and 36 males. [#permalink] New post 25 May 2013, 14:27
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Lake A has a duck population of 30 females and 36 males. Lake B’s duck population consists of the same ratio of females to males. If 6 new female ducks are added to Lake B and no other ducks are added or removed, the new total duck population of Lake B could be which of the following?

A. 144
B. 105
C. 78
D. 51
E. 36
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 25 May 2013, 14:34
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yogirb8801 wrote:
Lake A has a duck population of 30 females and 36 males. Lake B’s duck population consists of the same ratio of females to males. If 6 new female ducks are added to Lake B and no other ducks are added or removed, the new total duck population of Lake B could be which of the following?

A. 144
B. 105
C. 78
D. 51
E. 36


The ratio of females to males in Lake B is 30:36 = 5:6 --> the total number of ducks in Lake B must be a multiple of (5+6)=11.

When 6 new female ducks are added to Lake B, the total number of ducks in Lake B becomes a multiple of 11 plus 6.

Only 105 is a multiple of 11 plus 6: 9*11+6=105.

Answer: B.

Hope it's clear.
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 25 May 2013, 14:46
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yogirb8801 wrote:
Lake A has a duck population of 30 females and 36 males. Lake B’s duck population consists of the same ratio of females to males. If 6 new female ducks are added to Lake B and no other ducks are added or removed, the new total duck population of Lake B could be which of the following?

A. 144
B. 105
C. 78
D. 51
E. 36


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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 27 May 2013, 03:18
Thanks Bunuel for explanation. very helpful.
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 29 May 2013, 08:32
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the ratio is 5:6
So let the female ducks be 5x and male be 6x.
Total duck=11x
Now 11x+6 should divide one of the options.
105-6=99
Therefore ans is B
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 31 May 2013, 12:40
I wrote a table down as following and checked which values could be plugged in

F. M. F+m+6
15 18 38
30 36 71
45 54 105 <--- stopped here
60 72
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 17 Aug 2013, 18:52
Why not a multiple of 17?
5 F to 6 M. If you add 6 F then 11 F to 6 M for a total of 17 ducks. So Lake B must have a multiple of 17 ducks?

How can it be a multiple of 11 if you add only female ducks? Once you add 6 female ducks, the ratio of F and M ducks changes!
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 17 Aug 2013, 19:20
manavkhurana wrote:
Why not a multiple of 17?
5 F to 6 M. If you add 6 F then 11 F to 6 M for a total of 17 ducks. So Lake B must have a multiple of 17 ducks?

How can it be a multiple of 11 if you add only female ducks? Once you add 6 female ducks, the ratio of F and M ducks changes!


Hi,

The female to male population is in the ratio 5:6. So the total duck population is 11x . It could be 11, 22 ,33 and so on. Now 6 female ducks are added to this population . In other words you are adding 6 to a multiple of 11. So the new duck population should be multiple of 11 + 6.

So the only choice that satisfies this requirement is 105 which is 99+6.

It is not a multiple of 17 because we do not have 11 female ducks for every 6 male ducks.
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 17 Aug 2013, 19:37
Got it, thanks a lot!

Basically, as you stated, we are just adding 6 ducks to the original amount of ducks in lake B. If it was a multiple of 17, there would be a lot more than 6 ducks added. We do not have 11 F per 5 M, we just have 6 more ducks overall.

Thanks again.
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 18 Aug 2013, 18:36
Bunuel wrote:
yogirb8801 wrote:
Lake A has a duck population of 30 females and 36 males. Lake B’s duck population consists of the same ratio of females to males. If 6 new female ducks are added to Lake B and no other ducks are added or removed, the new total duck population of Lake B could be which of the following?

A. 144
B. 105
C. 78
D. 51
E. 36


The ratio of females to males in Lake B is 30:36 = 5:6 --> the total number of ducks in Lake B must be a multiple of (5+6)=11.

When 6 new female ducks are added to Lake B, the total number of ducks in Lake B becomes a multiple of 11 plus 6.

Only 105 is a multiple of 11 plus 6: 9*11+6=105.

Answer: B.

Hope it's clear.


Hi,

I am not able to understand the question properly.

Q says the Lake population is 30 females and 36 males. and for Lake B population the Ratio of male to female is is same. i.e. 3:3.

its nowhere mentioned as Lake B population is of same ratio as Lake A.

please clarify mine plz.

Regards,
Rrsnathan.
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 19 Aug 2013, 00:46
Expert's post
rrsnathan wrote:
Bunuel wrote:
yogirb8801 wrote:
Lake A has a duck population of 30 females and 36 males. Lake B’s duck population consists of the same ratio of females to males. If 6 new female ducks are added to Lake B and no other ducks are added or removed, the new total duck population of Lake B could be which of the following?

A. 144
B. 105
C. 78
D. 51
E. 36


The ratio of females to males in Lake B is 30:36 = 5:6 --> the total number of ducks in Lake B must be a multiple of (5+6)=11.

When 6 new female ducks are added to Lake B, the total number of ducks in Lake B becomes a multiple of 11 plus 6.

Only 105 is a multiple of 11 plus 6: 9*11+6=105.

Answer: B.

Hope it's clear.


Hi,

I am not able to understand the question properly.

Q says the Lake population is 30 females and 36 males. and for Lake B population the Ratio of male to female is is same. i.e. 3:3.

its nowhere mentioned as Lake B population is of same ratio as Lake A.

please clarify mine plz.

Regards,
Rrsnathan.


Please read the questions carefully:

Lake A has a duck population of 30 females and 36 males --> the ratio is F:M = 30:36 = 5:6.
Lake B’s duck population consists of the same ratio of females to males --> F:M = 5:6.
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COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 26 Sep 2014, 13:19
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 28 Sep 2014, 23:56
yogirb8801 wrote:
Lake A has a duck population of 30 females and 36 males. Lake B’s duck population consists of the same ratio of females to males. If 6 new female ducks are added to Lake B and no other ducks are added or removed, the new total duck population of Lake B could be which of the following?

A. 144
B. 105
C. 78
D. 51
E. 36



As mentioned in earlier posts, we have to find answer by subtracting 6 from all 5 options & check if the resultant is divisible by 11?

What I did is, instead of subtracting 6, added 5 to all the 5 options

(Addition goes more easy with me; only result remains the same)


A. 144+5 = 149 (Not divisible by 11)

B: 105+5 = 110 (Yes we got it)

Answer = B
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Re: Lake A has a duck population of 30 females and 36 males. [#permalink] New post 11 Oct 2014, 09:41
hix...i thought lake B has the same ratio means 50:50 male and female ducks....blazz
Re: Lake A has a duck population of 30 females and 36 males.   [#permalink] 11 Oct 2014, 09:41
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