• 5 Day FREE Trial
Study Smarter, Not Harder

Available with Beat the GMAT members only code

• FREE GMAT Exam
Know how you'd score today for $0 Available with Beat the GMAT members only code • Award-winning private GMAT tutoring Register now and save up to$200

Available with Beat the GMAT members only code

• Free Practice Test & Review
How would you score if you took the GMAT

Available with Beat the GMAT members only code

• Free Trial & Practice Exam
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• 1 Hour Free
BEAT THE GMAT EXCLUSIVE

Available with Beat the GMAT members only code

• Magoosh
Study with Magoosh GMAT prep

Available with Beat the GMAT members only code

• Free Veritas GMAT Class
Experience Lesson 1 Live Free

Available with Beat the GMAT members only code

• 5-Day Free Trial
5-day free, full-access trial TTP Quant

Available with Beat the GMAT members only code

• Get 300+ Practice Questions

Available with Beat the GMAT members only code

xy is a 2 digit integer whose reverse. . .

This topic has 1 expert reply and 0 member replies

Top Member

Vincen Legendary Member
Joined
07 Sep 2017
Posted:
654 messages
Followed by:
3 members
6

xy is a 2 digit integer whose reverse. . .

Fri Sep 22, 2017 10:08 am
xy is a 2 digit integer whose reverse, yx, is x less than twice xy. What is the sum of x and y?

A) 8
B) 9
C) 11
D) 12
E) 13

The OA is E.

What formula solves this PS question? I couldn't establish it.

GMAT/MBA Expert

Jay@ManhattanReview GMAT Instructor
Joined
22 Aug 2016
Posted:
1063 messages
Followed by:
22 members
470
Sun Sep 24, 2017 4:32 am
Vincen wrote:
xy is a 2 digit integer whose reverse, yx, is x less than twice xy. What is the sum of x and y?

A) 8
B) 9
C) 11
D) 12
E) 13

The OA is E.

What formula solves this PS question? I couldn't establish it.
The 2-digit number [xy] can be represented as 10x + y, thus, its reverse [yx] = 10y + x

We are given that [yx] = 2*[xy] - x

10y + x = 2(10x + y) - x

4y = 9x

Since 4 and 9 are co-prime, and x and y are single-digit numbers, only possible values of x = 4 and y = 9.

Thus, the sum of the digits = 4 + 9 = 13.

Hope this helps!

-Jay
_________________
Manhattan Review GMAT Prep

Locations: New York | Hyderabad | Mexico City | Toronto | and many more...

Top First Responders*

1 GMATGuruNY 67 first replies
2 Rich.C@EMPOWERgma... 44 first replies
3 Brent@GMATPrepNow 40 first replies
4 Jay@ManhattanReview 25 first replies
5 Terry@ThePrinceto... 10 first replies
* Only counts replies to topics started in last 30 days
See More Top Beat The GMAT Members

Most Active Experts

1 GMATGuruNY

The Princeton Review Teacher

132 posts
2 Rich.C@EMPOWERgma...

EMPOWERgmat

112 posts
3 Jeff@TargetTestPrep

Target Test Prep

95 posts
4 Scott@TargetTestPrep

Target Test Prep

92 posts
5 Max@Math Revolution

Math Revolution

91 posts
See More Top Beat The GMAT Experts