GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 16 Jan 2019, 00:13

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

## Events & Promotions

###### Events & Promotions in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
• ### The winning strategy for a high GRE score

January 17, 2019

January 17, 2019

08:00 AM PST

09:00 AM PST

Learn the winning strategy for a high GRE score — what do people who reach a high score do differently? We're going to share insights, tips and strategies from data we've collected from over 50,000 students who used examPAL.
• ### Free GMAT Strategy Webinar

January 19, 2019

January 19, 2019

07:00 AM PST

09:00 AM PST

Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.

# To estimate the population of horned lizards in a national park, a tea

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 52119
To estimate the population of horned lizards in a national park, a tea  [#permalink]

### Show Tags

18 Apr 2018, 17:26
00:00

Difficulty:

(N/A)

Question Stats:

88% (01:58) correct 12% (02:45) wrong based on 27 sessions

### HideShow timer Statistics

To estimate the population of horned lizards in a national park, a team from the park service captures and tags 25 horned lizards and then releases the tagged lizards back into the park. Two weeks later, the team returns and captures 20 horned lizards, 4 of which bear tags that identify them as being among the previously captured lizards. If all the tagged lizards have dispersed throughout the park an are still active when the second group of lizards is captured, what is the best estimate of the horned lizard population in the park, based on the information obtained through this capture-tagr-ecapture strategy?

(A) 250
(B) 125
(C) 100
(D) 80
(E) 75

_________________
Intern
Joined: 18 Jul 2016
Posts: 34
Re: To estimate the population of horned lizards in a national park, a tea  [#permalink]

### Show Tags

18 Apr 2018, 19:02
I just want to give it a try.

1. Total Tagged horned lizard = 25
2. Two weeks after team captures 20 lizards, of which 4 lizards are already tagged (from previously captured lizards)
=> $$\frac{{Untagged Horned Lizard}}{{tagged Horned Lizard}}$$ = $$\frac{16}{4}$$ = $$\frac{4}{1}$$

=> Total Untagged Horned Lizard = $$\frac{4}{1}$$* Total Tagged horned lizard
= $$\frac{4}{1} * 25$$
= 100

Hence Total Horned Lizard = Tagged Lizard + Untagged Lizard = 25 + 100 = 125
Senior SC Moderator
Joined: 22 May 2016
Posts: 2329
To estimate the population of horned lizards in a national park, a tea  [#permalink]

### Show Tags

19 Apr 2018, 14:57
Bunuel wrote:
To estimate the population of horned lizards in a national park, a team from the park service captures and tags 25 horned lizards and then releases the tagged lizards back into the park. Two weeks later, the team returns and captures 20 horned lizards, 4 of which bear tags that identify them as being among the previously captured lizards. If all the tagged lizards have dispersed throughout the park an are still active when the second group of lizards is captured, what is the best estimate of the horned lizard population in the park, based on the information obtained through this capture-tagr-ecapture strategy?

(A) 250
(B) 125
(C) 100
(D) 80
(E) 75

Of 20 lizards caught the second time, 4 are tagged, which constitutes
$$\frac{4}{20}=.20*100=20$$ percent of the lizards caught

That's a sample of the whole lizard population.

The total number of tagged lizards, now dispersed, should be represented in the whole population in the same percent, roughly, as the percent of tagged lizards sample (the second catch.)

25 tagged lizards = .20 of all lizards

All lizards = $$\frac{25}{.2}= 125$$ lizards

_________________

Never look down on anybody unless you're helping them up.
--Jesse Jackson

Target Test Prep Representative
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2830
Re: To estimate the population of horned lizards in a national park, a tea  [#permalink]

### Show Tags

23 Apr 2018, 15:57
Bunuel wrote:
To estimate the population of horned lizards in a national park, a team from the park service captures and tags 25 horned lizards and then releases the tagged lizards back into the park. Two weeks later, the team returns and captures 20 horned lizards, 4 of which bear tags that identify them as being among the previously captured lizards. If all the tagged lizards have dispersed throughout the park an are still active when the second group of lizards is captured, what is the best estimate of the horned lizard population in the park, based on the information obtained through this capture-tagr-ecapture strategy?

(A) 250
(B) 125
(C) 100
(D) 80
(E) 75

Let’s let x = the total population of horned lizards in the park. We know that 25 of those x lizards were tagged. Thus, after the tagging, the ratio of tagged lizards to total population is 25/x. Two weeks later, we know that 4 of the 20 lizards captured were tagged. To estimate the total population, it is assumed that the ratio of tagged lizards to total lizards in the group of 20 captured lizards (which is 4/20) is the same as the earlier ratio of 25/x. Thus, we can create the proportion:

4/20 = 25/x

4x = 500

x = 125

_________________

Jeffery Miller

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: To estimate the population of horned lizards in a national park, a tea &nbs [#permalink] 23 Apr 2018, 15:57
Display posts from previous: Sort by

# To estimate the population of horned lizards in a national park, a tea

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.