BTGModeratorVI wrote: ↑

Tue Feb 18, 2020 10:54 am

Of the 120 passengers on Flight 750, 50% are female. 10% of the passengers sit in first class, and the rest of the passengers sit in coach class. If 1/3 of the passengers in first class are male, how many females are there in coach class?

A. 44
B. 48
C. 50
D. 52
E. 56

Source: Manhattan Prep
Answer: D

Given that there are 50% females, there are 50% of 120 = 60 females

Since 10% of the passengers are from I class, there are 10% 0f 120 = 12 passengers are from I class

Since 1/3 of the I class passengers are males, there are 1/3 of 12 = 4 male I class passengers; thus, there are 12 – 4 = 8 female I class passengers

=> No. of female coach passengers = 60 – 8 = 52

The correct answer: [spoiler][/spoiler]

Hope this helps!

-Jay
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BTGModeratorVI wrote: ↑

Tue Feb 18, 2020 10:54 am

Of the 120 passengers on Flight 750, 50% are female. 10% of the passengers sit in first class, and the rest of the passengers sit in coach class. If 1/3 of the passengers in first class are male, how many females are there in coach class?

A. 44
B. 48
C. 50
D. 52
E. 56

Source: Manhattan Prep
Answer: D

We can also solve this question by using a technique called 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 (aka overlapping sets questions)..
Here, we have a population of passengers, and the two characteristics are:
- male or female
- first class or coach class

Of the 120 passengers on Flight 750, 50% are female. 10% of the passengers sit in first class, and the rest of the passengers sit in coach class.
With this information we can set up our diagram as follows:


1/3 of the passengers in first class are male
We already know that there are 12 passengers in first class
1/3 of 12 = 4, so there are 4 male passengers in first class
So we get:


At this point we can fill in the remaining boxes to get:


How many females are there in coach class?
The yellow box above denotes the number of females in coach class
So we can see that there are 52 females in coach class

Answer: D

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