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Source: Official Guide for GMAT Review 2016 Problem Solving; #216

1

If a two-digit positive integer has its

If a two-digit positive integer has its digits reversed, the resulting integer differs from the original by 27. By how much do the two digits differ?

2 Explanations

1

PRANAVA SHEORAN

Let the number be ab, where a is the digit at 10s place and b is the digit at ones place. The number formed by reversing the digits of ab is ba. Note that ab = 10a+b and ba = 10b+a. So (ab - ba) = [(10a+b)-(10b+a)] = [9(a-b)]. Since the difference of 2 numbers is 27 , 9(a-b) = 27. Therefore, (a-b) =3

Nov 4, 2016 • Comment

Sam Kinsman

That's right Pranava! Good job solving this one, and thanks for sharing your answer! :D

Nov 4, 2016 • Reply

1

Gravatar Mike McGarry, Magoosh Tutor

Aug 17, 2015 • Comment

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Official Guide for GMAT Review 2016

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Official Guide for the GMAT 12th Ed.

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Section 5.3 Problem Solving

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