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

 It is currently 21 Oct 2018, 10:11

### 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

# If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 50009
If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is  [#permalink]

### Show Tags

04 May 2017, 03:35
1
1
00:00

Difficulty:

15% (low)

Question Stats:

95% (00:57) correct 5% (01:01) wrong based on 62 sessions

### HideShow timer Statistics

If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is the product xy?

A. 108
B. 84
C. 21
D. 12
E. 9

_________________
CEO
Joined: 12 Sep 2015
Posts: 3021
Re: If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is  [#permalink]

### Show Tags

04 May 2017, 06:30
Top Contributor
Bunuel wrote:
If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is the product xy?

A. 108
B. 84
C. 21
D. 12
E. 9

The sum of x and y is 21
So, x + y = 21

The ratio of x to y is 3 to 4
So, x/y = 3/4

Take x + y = 21 and solve for x to get x = 21 - y
Now take x/y = 3/4 and replace x with (21-y) to get: (21-y)/y = 3/4
Cross multiply: 4(21-y) = 3y
Expand: 84 - 4y = 3y
Solve: y = 12
Since x + y = 21, we can conclude that x = 9

So, xy = (9)(12) = 108

Cheers,
Brent
_________________

Brent Hanneson – GMATPrepNow.com

Manager
Joined: 05 Nov 2016
Posts: 89
Re: If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is  [#permalink]

### Show Tags

04 May 2017, 07:11
by looking into the sum 21, the numbers are below 21, with average 3:4.. possible values could be 3,4 or 6,8(ruled out since the sum is odd, for the sum to be odd, atleast one should be odd) and 9,12.. this satisfies the condition
Hence 12*9 = 108
_________________

Kudos are always welcome ... as well your suggestions

Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4095
Location: India
GPA: 3.5
Re: If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is  [#permalink]

### Show Tags

04 May 2017, 09:30
Bunuel wrote:
If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is the product xy?

A. 108
B. 84
C. 21
D. 12
E. 9

Quote:
The ratio of x to y is 3 to 4,
x : y = 3a : 4a

Aga, it is given -

Quote:
The sum of x and y is 21

So, 3a + 4a = 21

Or, 7a = 21

Or, a = 3

Thus, the product of xy is 3a*4a => (3*3)(4*3) = 108

Hence, answer must be (A) 108
_________________

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 )

Target Test Prep Representative
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 3896
Location: United States (CA)
Re: If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is  [#permalink]

### Show Tags

06 May 2017, 18:01
1
Bunuel wrote:
If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is the product xy?

A. 108
B. 84
C. 21
D. 12
E. 9

We can create an equation and ratio.

x + y = 21

and

x : y = 3n : 4n

Thus:

3n + 4n = 21

7n = 21

n = 3

So, x = 3(3) = 9 and y = 4(3) = 12.

Therefore, the product of x and y is xy = (9)(12) = 108.

_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Re: If the sum of x and y is 21 and the ratio of x to y is 3 to 4, what is &nbs [#permalink] 06 May 2017, 18:01
Display posts from previous: Sort by