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# Of the goose eggs laid at a certain pond, 2/3 hatched and 3/

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Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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30 Jan 2014, 01:55
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The Official Guide For GMAT® Quantitative Review, 2ND Edition

Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 of the geese that hatched from those eggs survived the first month. Of the geese that survived the first month, 3/5 did not survive the first year. If 120 geese survived the first year and if no more than one goose hatched from each egg, how many goose eggs were laid at the pond?

(A) 280
(B) 400
(C) 540
(D) 600
(E) 840

Problem Solving
Question: 69
Category: Arithmetic Operations with rational numbers
Page: 70
Difficulty: 600

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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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30 Jan 2014, 01:55
1
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SOLUTION

Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 of the geese that hatched from those eggs survived the first month. Of the geese that survived the first month, 3/5 did not survive the first year. If 120 geese survived the first year and if no more than one goose hatched from each egg, how many goose eggs were laid at the pond?

(A) 280
(B) 400
(C) 540
(D) 600
(E) 840

Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 of the geese that hatched from those eggs survived the first month:
2/3*3/4 = 1/2 survived the first month.

Of the geese that survived the first month, 3/5 did not survive the first year:
(1-3/5)*1/2 = 1/5 survived the first year.

120 geese survived the first year:

1/5*(total) = 120 --> (total) = 600.

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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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30 Jan 2014, 03:01
3
Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 f the geese that hatched from those eggs survived the first month.Of the geese that survived the first month, 3/5 did not survive the first year. If 120 geese survived the first year and if no more than one goose hatched from each egg, how many goose eggs were laid at the pond?

(A) 280
(B) 400
(C) 540
(D) 600
(E) 840

Sol: Plugging in answer choices is best bet
540 eggs laid ----> 2/3 hatached so 540*2/3 = 360 and 3/4 of these eggs survived the first month so 3/4*360=270 survived and out of these 2/5 survived the first year. so 270*2/5=96...But is given that 120 geese survived so no of eggs laid must be more than 540 so

Lets take D and check 6000----> 2/3h hatched (400) of these 3/4 survived first month is 300 and out 300 2.5 survied first year which 2/5*300=120----> same as stated in the Question.

So Ans D

600 level is okay
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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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30 Jan 2014, 03:04
1
choice D.
Let the total geese be x
Given:x*(2/3)*(3/4)*(2/5)=120
Therefore,x/5=120
x=600
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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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05 Dec 2014, 01:25
1
I used a bit different approach. The total must be LCM of 3, 4, and 5 or else, fraction won't make to 120. This means whatever the total is, it must be multiple of 60. I started with 540 and landed with 112 instead of 120 and I went on to mark 600. Is this approach correct?

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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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05 Dec 2014, 02:11
1
Let the goose eggs laid at pond = x

Total hatched $$= \frac{2x}{3}$$

Survived in 1st month $$= \frac{2x}{3} * \frac{3}{4} = \frac{x}{2}$$

Not surviving 1st year $$= \frac{x}{2} * \frac{3}{5} = \frac{3x}{10}$$

Surviving 1st year $$= \frac{5x}{10} - \frac{3x}{10} = \frac{2x}{10}$$

Given that $$\frac{2x}{10} = 120$$

x = 120*5 = 600

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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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28 Sep 2016, 03:27
[quote="Bunuel"]The Official Guide For GMAT® Quantitative Review, 2ND Edition

Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 of the geese that hatched from those eggs survived the first month. Of the geese that survived the first month, 3/5 did not survive the first year. If 120 geese survived the first year and if no more than one goose hatched from each egg, how many goose eggs were laid at the pond?

(A) 280
(B) 400
(C) 540
(D) 600
(E) 840

number of eggs = x

survaivers= $$120=(\frac{2}{3}*\frac{3}{4}*(1-\frac{3}{5})*)x$$

$$\frac{1}{5} *x =120$$
$$x=600$$

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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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28 Sep 2016, 16:43
1
Plug in numbers

I started with D instead of B since it is a multiple of 3

So if 600 eggs then 400 hatched (2/3) then 300 survived (3/4) and 120 (2/5) survived the first year

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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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29 May 2017, 23:09
Bunuel wrote:
The Official Guide For GMAT® Quantitative Review, 2ND Edition

Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 of the geese that hatched from those eggs survived the first month. Of the geese that survived the first month, 3/5 did not survive the first year. If 120 geese survived the first year and if no more than one goose hatched from each egg, how many goose eggs were laid at the pond?

(A) 280
(B) 400
(C) 540
(D) 600
(E) 840

Problem Solving
Question: 69
Category: Arithmetic Operations with rational numbers
Page: 70
Difficulty: 600

GMAT Club is introducing a new project: The Official Guide For GMAT® Quantitative Review, 2ND Edition - Quantitative Questions Project

Each week we'll be posting several questions from The Official Guide For GMAT® Quantitative Review, 2ND Edition and then after couple of days we'll provide Official Answer (OA) to them along with a slution.

We'll be glad if you participate in development of this project:
2. Please vote for the best solutions by pressing Kudos button;
3. Please vote for the questions themselves by pressing Kudos button;
4. Please share your views on difficulty level of the questions, so that we have most precise evaluation.

Thank you!

This problem tests your ability to work backwards.

120 geese survived each phase.

x*2/3 = eggs that were hatched.

x*2/3*3/4 = eggs that were hatched and survived the first month

x*2/3*3/4*2/5 = eggs that were hatched, survived the first month, and survived the first year

x*2/3*3/4*2/5 = 120

x/3*3/2*2/5 = 120

x/5 = 120

x = 500 + 100 = 600.
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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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01 Jun 2017, 10:24
Quote:

Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 of the geese that hatched from those eggs survived the first month. Of the geese that survived the first month, 3/5 did not survive the first year. If 120 geese survived the first year and if no more than one goose hatched from each egg, how many goose eggs were laid at the pond?

(A) 280
(B) 400
(C) 540
(D) 600
(E) 840

We can let n = the total number of goose eggs.

We are given that 2/3 of the eggs hatched and 3/4 of the geese that hatched from those eggs survived the first month, and of the geese that survived the first month, 3/5 did not survive the first year (which means that ⅖ did survive the first year). We are also given that a total of 120 geese survived the first year. Thus:

n(2/3)(3/4)(2/5) = 120

12n/60 = 120

n/5 = 120

n = 600

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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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10 Mar 2018, 03:48
Bunuel wrote:
SOLUTION

Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 of the geese that hatched from those eggs survived the first month. Of the geese that survived the first month, 3/5 did not survive the first year. If 120 geese survived the first year and if no more than one goose hatched from each egg, how many goose eggs were laid at the pond?

(A) 280
(B) 400
(C) 540
(D) 600
(E) 840

Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 of the geese that hatched from those eggs survived the first month:
2/3*3/4 = 1/2 survived the first month.

Of the geese that survived the first month, 3/5 did not survive the first year:
(1-3/5)*1/2 = 1/5 survived the first year.

120 geese survived the first year:

1/5*(total) = 120 --> (total) = 600.

Hi Bunuel

can you help me to understand one detail in your solution ? please

ok here all is clear (2/3*3/4 = 1/2 survived the first month.)

but here
Of the geese that survived the first month, 3/5 did not survive the first year:
(1-3/5)*1/2 = 1/5 survived the first year.

why are you subtracting 3/5 from 1 and not just multiplying 3/5 by 1/2 ? as you did in fest step ... can you explan ?

thanks !
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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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10 Mar 2018, 04:11
1
dave13 wrote:
Bunuel wrote:
SOLUTION

Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 of the geese that hatched from those eggs survived the first month. Of the geese that survived the first month, 3/5 did not survive the first year. If 120 geese survived the first year and if no more than one goose hatched from each egg, how many goose eggs were laid at the pond?

(A) 280
(B) 400
(C) 540
(D) 600
(E) 840

Of the goose eggs laid at a certain pond, 2/3 hatched and 3/4 of the geese that hatched from those eggs survived the first month:
2/3*3/4 = 1/2 survived the first month.

Of the geese that survived the first month, 3/5 did not survive the first year:
(1-3/5)*1/2 = 1/5 survived the first year.

120 geese survived the first year:

1/5*(total) = 120 --> (total) = 600.

Hi Bunuel

can you help me to understand one detail in your solution ? please

ok here all is clear (2/3*3/4 = 1/2 survived the first month.)

but here
Of the geese that survived the first month, 3/5 did not survive the first year:
(1-3/5)*1/2 = 1/5 survived the first year.

why are you subtracting 3/5 from 1 and not just multiplying 3/5 by 1/2 ? as you did in fest step ... can you explan ?

thanks !

Hi dave13

The reason for doing that is the wording which reads "of the geese that survived the first month, 3/5 did not survive"
which when translated gives us $$\frac{1}{2} - \frac{1}{2}*\frac{3}{5}$$ or $$\frac{1}{2} - \frac{3}{10} = \frac{2}{10} = \frac{1}{5}$$ will survive!

We could also write the equation as 1/2*(1 - 3/5)

Hope this helps you!
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Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/  [#permalink]

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18 Aug 2018, 20:41
1
Hi dave13

I have seen may similar Official problems . While i use this approach for a variety of problems, but practicing it would help us problems involving percents/ratio/fractions.
So, lets take a suitable number . That number should be a an integer. Since Eggs cant be laid in fractions.
How to choose a number .
First that number can be LCM of 3,4,5 which is 60
of 60 Eggs 2/3 hatched = 40 Hatched into geese

of40 Geese 3/4 of the geese survived first month= 30 Survived first month

Now If 3/5 did not survive the first year, then 1/5 survived first year

Of 30 geeses survived first month 1/5 did not survive the first year=12

Ok we are given that 120 survived first year out of what ever eggs were laid . we found that 12 survived out of 60 eggs .
laid

So 60*10 eggs laid and of these 12*10 Survived first year.

600 Choice D
Re: Of the goose eggs laid at a certain pond, 2/3 hatched and 3/ &nbs [#permalink] 18 Aug 2018, 20:41
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