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

This topic has expert replies
Moderator
Posts: 2048
Joined: 15 Oct 2017
Followed by:6 members
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

The OA is D.

I tried to solve it in this way

Let the total eggs laid = x

Then x*(2/3)*(3/4)*(3/5) is the no of eggs who didn't survive

So, eggs who survived = x - 3x / 10 = 120

This doesn't give the correct answer.

Please, can anyone assist me to solve this PS question? Thanks!

User avatar
GMAT Instructor
Posts: 15537
Joined: 25 May 2010
Location: New York, NY
Thanked: 13060 times
Followed by:1901 members
GMAT Score:790

by GMATGuruNY » Tue Apr 03, 2018 7:18 pm
BTGmoderatorLU wrote: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 PLUG IN THE ANSWERS, which represent the total number of eggs.
When the correct answer is plugged in, the number of geese that survive the first year = 120.
The fractions in the prompt -- 2/3, 3/4 and 3/5 -- imply that the correct answer that the correct answer must be a multiple of 3, 4 and 5.
Since A and B are not divisible by 3, eliminate A and B.

D: 600 eggs
Since 2/3 of the eggs hatched, the number of eggs that hatched = (2/3)(600) = 400.
Since 3/4 of the geese from the hatched eggs survived the first month, the number of geese that survived the first month = (3/4)(400) = 300.
Since 3/5 of the first-month survivors did NOT survive the first year, 2/5 of the first-month survivors SURVIVED the first year:
(2/5)(300) = 120.
Success!

The correct answer is D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 1462
Joined: 09 Apr 2015
Location: New York, NY
Thanked: 39 times
Followed by:21 members

by [email protected] » Fri Apr 06, 2018 7:53 am
BTGmoderatorLU wrote: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 that were originally laid.

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 2/5 did survive the first year). We are also given that a total of 120 geese survived the first year. Thus, we can create a "survival" equation:

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

12n/60 = 120

n/5 = 120

n = 600

Answer: D

Jeffrey Miller
Head of GMAT Instruction
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

Legendary Member
Posts: 2083
Joined: 29 Oct 2017
Followed by:6 members

by swerve » Fri Apr 06, 2018 11:38 am
Hi BTGmoderatorLU,

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. OptionD.

Regards!

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16084
Joined: 08 Dec 2008
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1267 members
GMAT Score:770
BTGmoderatorLU wrote:
Tue Apr 03, 2018 6:15 pm
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
STRATEGY: Upon reading any GMAT Problem Solving question, we should always ask, Can I use the answer choices to my advantage?
In this case, we can easily test the answer choices.
From here, I'd typically give myself up to 20 seconds to identify a faster approach, but I can already see that I can immediately in lemonade to answer choices, which means I only need to test one answer choice.


We’re told that 2/3 of the goose eggs laid hatch.
Since the answer choices tell us the number of goose eggs laid, we can immediately eliminate choices A and B since 2/3 of 280 and 2/3 of 400 don’t result in integer values (and this real world question doesn’t allow for fractional hatchlings!).

From here, we’ll test choice D (the middle remaining choice). If it works, we’re done. If we end up with more than 120 geese, then the correct answer must be C. If we end up with fewer than 120 geese, then the correct answer must be E.

(D) 600 This tells us the number of goose eggs we start with.
Given: 2/3 of the eggs hatched. So, the total number of hatchlings = 2/3 of 600 = 400
Given: 3/4 of the hatchlings survived the first month. So, the number of 1st month survivors = 3/4 of 400 = 300
Given: Of the geese that survived the first month, 3/5 did not survive the first year, which means 2/5 of those geese survived.. So, the number of survivors = 2/5 of 300 = 120
Perfect!! This matches the information in the question.

Answer: D
Brent Hanneson - Creator of GMATPrepNow.com
Image