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place value of numbers

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place value of numbers

by topspin360 » Sat Aug 04, 2012 8:28 pm
any way to solve this problems using place value of numbers (100A + 10B + C = ABC)? im using that framework for this kind of problems. it usually works but for some reason cant figure it out for this one..

If A , B , and C are digits and AB does not = 0, what is the value of B?

(1) AB + BA = AAC

(2) A = 1

A) 1 is sufficient
B) 2 is sufficient
C) Both 1 and 2 sufficient together
D) 1 and 2 sufficient individually
E) not sufficient
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Source: — Data Sufficiency |
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by eagleeye » Sat Aug 04, 2012 8:47 pm
topspin360 wrote:any way to solve this problems using place value of numbers (100A + 10B + C = ABC)? im using that framework for this kind of problems. it usually works but for some reason cant figure it out for this one..

If A , B , and C are digits and AB does not = 0, what is the value of B?

(1) AB + BA = AAC

(2) A = 1

A) 1 is sufficient
B) 2 is sufficient
C) Both 1 and 2 sufficient together
D) 1 and 2 sufficient individually
E) not sufficient
Of course, you can still use this framework.

Statement 1:
First off, since adding two digits is giving a 3 digit number A has to be 1( the only possible carry over digit). We can dismiss statement 2 right here as it doesn't add anything different. As A=1,
AB = 10*1 + B
BA = 10B + 1
AAC = 100+10+C = 110 + C
AB+BA = AAC

Now using the framework : AB + BA = 11 + 11B = 110 + C
=> 11B = 99 + C
=> B = 9 + C/11.
Since B is an integer and C is less than 11, C must be 0.
Then B = 9.
Sufficient.

2) is insufficient as I said earlier
A is correct :)
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by Anurag@Gurome » Sat Aug 04, 2012 8:57 pm
topspin360 wrote:any way to solve this problems using place value of numbers (100A + 10B + C = ABC)? im using that framework for this kind of problems. it usually works but for some reason cant figure it out for this one..

If A , B , and C are digits and AB does not = 0, what is the value of B?

(1) AB + BA = AAC

(2) A = 1

A) 1 is sufficient
B) 2 is sufficient
C) Both 1 and 2 sufficient together
D) 1 and 2 sufficient individually
E) not sufficient
(1) AB + BA = AAC

If A = 1 then 1B + B1 = 11C or B = 9 (B can not be less than 8 as 18 + 81 = 99, which is not a three digit number) and 19 + 91 = 110; SUFFICIENT.

(2) A = 1 is clearly Not SUFFICIENT.

The correct answer is A.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

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