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## 500 ps test23 #15

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dunkin77 Really wants to Beat The GMAT!
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500 ps test23 #15 Mon Apr 16, 2007 12:02 pm
Elapsed Time: 00:00
• Lap #[LAPCOUNT] ([LAPTIME])
15. If the tens digit x and the units digit y of a positive integer n are reversed, the resulting integer is 9 more than n. What is y in terms of x ?
(A) 10 - x
(B) 9 - x
(C) x + 9
(D) x - 1
(E) x + 1

Hi,

I though the answer is D) but turned out to be E). Can anyone explain why??

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jayhawk2001 Community Manager
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Mon Apr 16, 2007 9:02 pm
dunkin77 wrote:
15. If the tens digit x and the units digit y of a positive integer n are reversed, the resulting integer is 9 more than n. What is y in terms of x ?
(A) 10 - x
(B) 9 - x
(C) x + 9
(D) x - 1
(E) x + 1

Hi,

I though the answer is D) but turned out to be E). Can anyone explain why??
n can be written as 10x + y

If we reverse x and y, we get a number of the form 10y + x

10y + x = 9 + 10x + y
9y = 9x + 9
y = x + 1

Cybermusings GMAT Destroyer!
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Tue Apr 17, 2007 3:25 am
Original number - 10x+y
New number - 10y+x
10y+x-10x-y=9
9y-9x=9
Y-x=1
y=x+1

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