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On a construction site, 16 of the men wear helmets, and 19

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On a construction site, 16 of the men wear helmets, and 19

by AAPL » Wed Jan 02, 2019 6:01 am

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Economist GMAT

On a construction site, 16 of the men wear helmets, and 19 of the women do not wear helmets. How many people are there on the construction site?

1) There are 21 men on the construction site.
2) There are 24 people that do not wear helmets on the construction site.

OA E
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Source: — Data Sufficiency |

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by Jay@ManhattanReview » Thu Jan 03, 2019 3:25 am

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AAPL wrote:Economist GMAT

On a construction site, 16 of the men wear helmets, and 19 of the women do not wear helmets. How many people are there on the construction site?

1) There are 21 men on the construction site.
2) There are 24 people that do not wear helmets on the construction site.

OA E
Pl. see this self-explanatory image.

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The correct answer: E

Hope this helps!

-Jay
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by Brent@GMATPrepNow » Thu Jan 03, 2019 9:43 am

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I thought I'd point out that Jay's approach is also known as the Double Matrix Method.
This technique can be used for most questions featuring a population in which each member has two characteristics associated with it.
Here, we have a population of construction worker, and the two characteristics are:
- male or female
- wears helmet or does not wear helmet

This question type is VERY COMMON on the GMAT, so be sure to master the technique.

To learn more about the Double Matrix Method, watch this video: https://www.gmatprepnow.com/module/gmat- ... ems?id=919

Once you're familiar with this technique, you can attempt these additional practice questions:

Easy Problem Solving questions
- https://www.beatthegmat.com/finance-majo ... 67425.html

Medium Problem Solving questions
- https://www.gmatprepnow.com/module/gmat- ... /video/920
- https://www.beatthegmat.com/posted-speed ... 72374.html
- https://www.beatthegmat.com/motel-t271938.html
- https://www.beatthegmat.com/of-the-appli ... 70255.html
- https://www.beatthegmat.com/opening-nigh ... 64869.html
- https://www.beatthegmat.com/at-least-100 ... 74669.html
- https://www.beatthegmat.com/prblem-solving-t279424.html

Difficult Problem Solving questions
- https://www.gmatprepnow.com/module/gmat- ... /video/946
- https://www.beatthegmat.com/ratio-problem-t268339.html
- https://www.beatthegmat.com/overlapping- ... 65223.html
- https://www.beatthegmat.com/fractions-t264254.html
- https://www.beatthegmat.com/overlapping- ... 64092.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-2

Easy Data Sufficiency questions
- https://www.gmatprepnow.com/module/gmat- ... /video/943
- https://www.beatthegmat.com/for-what-per ... 70596.html
- https://www.beatthegmat.com/ds-quest-t187706.html

Medium Data Sufficiency questions
- https://www.beatthegmat.com/sets-matrix-ds-t271914.html
- https://www.beatthegmat.com/each-of-peop ... 71375.html
- https://www.beatthegmat.com/a-manufacturer-t270331.html
- https://www.beatthegmat.com/in-costume-f ... 69355.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-1

Difficult Data Sufficiency questions
- https://youtu.be/dsCeqF9Kbk8
- https://www.beatthegmat.com/double-set-m ... 71423.html
- https://youtu.be/dOZ9KM1m5Hs
- https://www.beatthegmat.com/sets-t269449.html
- https://www.beatthegmat.com/mba/2011/05/ ... question-3

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by deloitte247 » Wed Jan 09, 2019 2:00 am

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Given;
16 men with helmet
19 women without helmet

To get the total number of people on site, we need to know either the total number of men and women or total number of people with helmet and people without helmet.

Statement 1--> There are 21 men on the construction site. This means that 5 men do not have helmet.
Also, there are 19 women without helmet but no information on the number of women with helmet or total no. of women.
Hence, Statement 1 is INSUFFICIENT

Statement 2 --> There are 24 people that do not wear helmets on the construction site. Out of the 24, 19 of them are women and 5 of them are men but there is no information on the total number of people with helmet. Hence, statement 2 is INSUFFICIENT.

Combining both statement together, we know the total number of men, but we do not know the total number of women.
Also, we know the total number of people without helmet but we do not know the total number of people with helmet.

Hence, the two statement together are INSUFFICIENT...

OPTION E is the correct answer.
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