It is currently 21 Oct 2017, 14:51

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# AB and BA are 2 digit integers and AB*BA=CDE, where CDE is a

Author Message
Senior Manager
Joined: 08 Aug 2005
Posts: 251

Kudos [?]: 64 [0], given: 0

AB and BA are 2 digit integers and AB*BA=CDE, where CDE is a [#permalink]

### Show Tags

09 Aug 2006, 03:48
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

AB and BA are 2 digit integers and AB*BA=CDE, where CDE is a 3 digit integer. What is AB?

1) A=E
2) A=C

Kudos [?]: 64 [0], given: 0

GMAT Instructor
Joined: 04 Jul 2006
Posts: 1259

Kudos [?]: 335 [0], given: 0

### Show Tags

09 Aug 2006, 06:24
getzgetzu wrote:
AB and BA are 2 digit integers and AB*BA=CDE, where CDE is a 3 digit integer. What is AB?

1) A=E
2) A=C

(10A+B)(10B+A)=100AB+10(A^2+B^2)+AB =100C+10D+E, neither A not B is equal to 0

(1) If A=E From above AB=E, so AB=A and B=1

But 31*13= 403 and 21*12=252, so clearly we don't know the value of B, it could be any of {1,2,3,4,5,6}

NOT SUFFICIENT

(2) If A=C, the hundreds digit of CDE is A, whereas the hundreds digit of AB*BA is at least AB. For these to be equal, it must be that B=1 and A^2+B^2=A^2+1 must be less than 10

Therefore A^2 is less than 9 i.e A is one of {1,2}

So number AB could be 11 or 21 as 11*11=121 and 21*12=252 satisfy (2). NOT SUFFICIENT

Notcing that if AB is 11 or 21, both (1) and (2) are met, I choose E. If A and B had to be different, (C) would be the answer AB=21, but this is not stated so cannot be assumed.

Kudos [?]: 335 [0], given: 0

Re: 2 digit integers   [#permalink] 09 Aug 2006, 06:24
Display posts from previous: Sort by