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

 It is currently 20 May 2019, 18:12

### 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

# In a group of children, the average (arithmetic mean) weight of the bo

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 55188
In a group of children, the average (arithmetic mean) weight of the bo  [#permalink]

### Show Tags

23 Aug 2018, 23:33
00:00

Difficulty:

15% (low)

Question Stats:

84% (01:35) correct 16% (02:06) wrong based on 61 sessions

### HideShow timer Statistics

In a group of children, the average (arithmetic mean) weight of the boys is 60 pounds, and the average weight of the girls is 48 pounds. If the average weight of all of the children in the group is 50 pounds, what is the ratio of the number of boys to the number of girls?

A. 1/12
B. 1/6
C. 1/5
D. 1/4
E. 1/3

_________________
Director
Joined: 18 Jul 2018
Posts: 898
Location: India
Concentration: Finance, Marketing
WE: Engineering (Energy and Utilities)
Re: In a group of children, the average (arithmetic mean) weight of the bo  [#permalink]

### Show Tags

23 Aug 2018, 23:39
2
Let the number of boys be X.
Let the number of girls be Y.
Now,
$$\frac{{60X+48Y}}{{X+Y}}$$ = 50.

Cross multiplying gives 60X+48Y = 50X+50Y
10X = 2Y
$$\frac{X}{Y}$$ = $$\frac{2}{10}$$ = $$\frac{1}{5}$$.

_________________
Press +1 Kudo If my post helps!
VP
Joined: 31 Oct 2013
Posts: 1352
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
Re: In a group of children, the average (arithmetic mean) weight of the bo  [#permalink]

### Show Tags

24 Aug 2018, 04:06
1
Bunuel wrote:
In a group of children, the average (arithmetic mean) weight of the boys is 60 pounds, and the average weight of the girls is 48 pounds. If the average weight of all of the children in the group is 50 pounds, what is the ratio of the number of boys to the number of girls?

A. 1/12
B. 1/6
C. 1/5
D. 1/4
E. 1/3

Through Allegation one can solve this one easily. 30 sec approach.
Attachments

Untitled.png [ 14.35 KiB | Viewed 826 times ]

Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4469
Location: India
GPA: 3.5
Re: In a group of children, the average (arithmetic mean) weight of the bo  [#permalink]

### Show Tags

24 Aug 2018, 08:04
Bunuel wrote:
In a group of children, the average (arithmetic mean) weight of the boys is 60 pounds, and the average weight of the girls is 48 pounds. If the average weight of all of the children in the group is 50 pounds, what is the ratio of the number of boys to the number of girls?

A. 1/12
B. 1/6
C. 1/5
D. 1/4
E. 1/3

$$60b + 48g = 50 (b + g)$$

Or, $$10b = 2g$$

So, $$5b = g$$

Or, $$b : g = 1 : 5$$, Answer must be (C)
_________________
Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )
EMPOWERgmat Instructor
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 14174
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: In a group of children, the average (arithmetic mean) weight of the bo  [#permalink]

### Show Tags

19 Mar 2019, 20:31
Hi All,

We're told that in a group of children, the average (arithmetic mean) weight of the boys is 60 pounds, the average weight of the girls is 48 pounds and the average weight of ALL of the children in the group is 50 pounds. We're asked for the ratio of the number of boys to the number of girls. This question can be solved in a number of different ways, including by TESTing THE ANSWERS. There's an interesting Number Property pattern that you can also take advantage of though (that can save you a bit of work REGARDLESS of which approach you use).

To start, since the average weight of ALL the children is 50 pounds, we know that the TOTAL weight of the children is a MULTIPLE OF 50... and that total ends in a '0.' Since the average weight of the boys is 60 pounds, we know that that sum will end in a '0.' The average weight of the girls is 48 pounds though, so will also need the total weight of this group to also be a multiple of 10... otherwise the sum of ALL the children won't end in a '0.' The only ways for that to occur are when the total number of girls is a MULTIPLE OF 5....

Looking at the answer choices, there's only one answer that fits... but here's how you can prove it's the correct answer by TESTing THE ANSWERS:

IF we have 1 boy and 5 girls...
then the total weight is 1(60) + 5(48) = 60 + 240 = 300
and the average weight is 300/6 = 50 pounds.
This fits what we were told, so the ratio MUST be 1:5 = 1/5

GMAT assassins aren't born, they're made,
Rich
_________________
760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

*****Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!*****

# Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save \$75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/
Re: In a group of children, the average (arithmetic mean) weight of the bo   [#permalink] 19 Mar 2019, 20:31
Display posts from previous: Sort by