In Mr. Smith's class, what is the ratio of

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jjjinapinch: Senior | Next Rank: 100 Posts; Posts: 83; Joined: Mon Jul 24, 2017 8:16 amFollowed by: 1 member

by jjjinapinch » Thu Jul 27, 2017 12:13 pm

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In Mr. Smith's class, what is the ratio of the number of boys to the number of girls?

(1) There are 3 times as many girls as boys in Mr. Smith's class.
(2) The number of boys is 1/4 of the total number of boys and girls in Mr. Smith's class.

Official Guide question
Answer: D

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by Brent@GMATPrepNow » Thu Jul 27, 2017 12:50 pm

jjjinapinch wrote:In Mr. Smith's class, what is the ratio of the number of boys to the number of girls?

(1) There are 3 times as many girls as boys in Mr. Smith's class.
(2) The number of boys is 1/4 of the total number of boys and girls in Mr. Smith's class.

Official Guide question
Answer: D

Target question: What is the ratio of the number of boys to the number of girls?

Statement 1: There are 3 times as many girls as boys in Mr. Smith's class.
This means there are 3 girls for every 1 boy
So, the ratio of the number of boys to the number of girls = 3 : 1
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: The number of boys is 1/4 of the total number of boys and girls in Mr. Smith's class.
So, for every 4 children there are 3 girls and 1 boy
So, the ratio of the number of boys to the number of girls = 3 : 1
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: D

Cheers,
Brent

Brent Hanneson - Creator of GMATPrepNow.com

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by [email protected] » Mon Mar 26, 2018 3:54 pm

Hi ALL,

We're asked for the ratio of the number of boys to the number of girls in Mr. Smith's Class. This question can be solved in a couple of different ways, including by TESTing VALUES.

1) There are 3 times as many girls as boys in Mr. Smith's class.

Based on the information in Fact 1, there could be....
1 boy and 3 girls, so the ratio is 1:3
2 boys and 6 girls, so the ratio is 2:6 = 1:3
3 boys and 9 girls, so the ratio is 3:9 = 1:3
Etc.
The ratio will ALWAYS be 1:3
Fact 1 is SUFFICIENT

2) The number of boys is 1/4 of the total number of boys and girls in Mr. Smith's class.

Based on the information in Fact 2, there could be....
1 boy and 4 total children (so there are 3 girls), so the ratio is 1:3
2 boys and 8 total children (so there are 6 girls), so the ratio is 2:6 = 1:3
3 boys and 12 total children (so there are 9 girls), so the ratio is 3: 9 = 1:3
Etc.
The ratio will ALWAYS be 1:3
Fact 2 is SUFFICIENT

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

Contact Rich at [email protected]

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Jeff@TargetTestPrep: GMAT Instructor; Posts: 1462; Joined: Thu Apr 09, 2015 9:34 amFollowed by: 22 members; Location: New York, NY; Thanked: 39 times

by Jeff@TargetTestPrep » Thu Jul 26, 2018 3:31 pm

jjjinapinch wrote:In Mr. Smith's class, what is the ratio of the number of boys to the number of girls?

(1) There are 3 times as many girls as boys in Mr. Smith's class.
(2) The number of boys is 1/4 of the total number of boys and girls in Mr. Smith's class.

We need to determine the ratio of the number of boys to the number of girls. If we denote the number of boys as b and the number of girls as g, we can say:

b/g = ?

Statement One Alone:

There are 3 times as many girls as boys in Mr. Smith's class.

We can create the equations:

g = 3b

g/b = 3

b/g = 1/3

Statement one is sufficient to answer the question.

Statement Two Alone:

The number of boys is 1/4 of the total number of boys and girls in Mr. Smith's class.

We can create the equation:

b = Â¼(b + g)

4b = b + g

3b = g

b/g = 1/3

Statement two is sufficient to answer the question.

Answer: D

Jeffrey Miller
Head of GMAT Instruction
[email protected]

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