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

 It is currently 20 Oct 2019, 17:56 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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  The average (arithmetic mean) score of a class was 70. If the boys’ av

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 58434
The average (arithmetic mean) score of a class was 70. If the boys’ av  [#permalink]

Show Tags 00:00

Difficulty:   35% (medium)

Question Stats: 78% (01:11) correct 22% (01:55) wrong based on 25 sessions

HideShow timer Statistics

The average (arithmetic mean) score of a class was 70. If the boys’ average was 65 and that of girls’ was 80, what could be the number of boys and girls, respectively, in the class?

(A) 8; 9
(B) 18; 27
(C) 9; 18
(D) 18; 9
(E) 5; 2

_________________
Senior PS Moderator V
Joined: 26 Feb 2016
Posts: 3335
Location: India
GPA: 3.12
Re: The average (arithmetic mean) score of a class was 70. If the boys’ av  [#permalink]

Show Tags

Bunuel wrote:
The average (arithmetic mean) score of a class was 70. If the boys’ average was 65 and that of girls’ was 80, what could be the number of boys and girls, respectively, in the class?

(A) 8; 9
(B) 18; 27
(C) 9; 18
(D) 18; 9
(E) 5; 2

Let the number of boys and girls be B and G respectively.

Using weighted average formula, we will get $$\frac{65B + 80G}{B + G} = 70$$

$$65B + 80G = 70B + 70G$$ -> $$10G = 5B$$ -> $$\frac{G}{B} = \frac{5}{10} = \frac{1}{2}$$ -> $$B = 2G$$

Therefore, a possibility for the number of boys and girls is 18;9(Option D)
_________________
You've got what it takes, but it will take everything you've got
VP  D
Joined: 31 Oct 2013
Posts: 1465
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
Re: The average (arithmetic mean) score of a class was 70. If the boys’ av  [#permalink]

Show Tags

Bunuel wrote:
The average (arithmetic mean) score of a class was 70. If the boys’ average was 65 and that of girls’ was 80, what could be the number of boys and girls, respectively, in the class?

(A) 8; 9
(B) 18; 27
(C) 9; 18
(D) 18; 9
(E) 5; 2

using Allegation Method:

70 - 65 = 5
80 - 70 = 10

Ratio: 10: 5 = 2 : 1 = 18 : 9.

The Best answer is D. Re: The average (arithmetic mean) score of a class was 70. If the boys’ av   [#permalink] 25 Sep 2018, 05:02
Display posts from previous: Sort by

The average (arithmetic mean) score of a class was 70. If the boys’ av

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne  