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# If x and y are positive integers and 1 + x + y + xy = 15,

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VP
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If x and y are positive integers and 1 + x + y + xy = 15, [#permalink]

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23 Jul 2007, 13:52
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If x and y are positive integers and 1 + x + y + xy = 15, what is the value of x + y?

A. 3
B. 5
C. 6
D. 8
E. 9

Senior Manager
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23 Jul 2007, 14:03
isolate variables on the right so:

x+y+xy=14

only two numbers that fit this (2 and 4)

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23 Jul 2007, 14:17
it should be C; its asking for X+Y (4+2)=6
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23 Jul 2007, 14:43
fresinha12 wrote:
it should be C; its asking for X+Y (4+2)=6

dang it. now would be a good time to state my RC isn't quite where I need it to be
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23 Jul 2007, 14:48
dang it me too
VP
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23 Jul 2007, 16:13
The OA is C
Thanks, guys!
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23 Jul 2007, 16:24
1+x+y+xy = (1+x)(1+y) =15
3*5 = 15 => x,y = {2,4}

Ans : 6
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23 Jul 2007, 19:25
1+x+y+xy = (1+x) + y(1+x) = (1+x)(1+y) = 15

Cannot be (1,15) because x would not be positive
Must be (3,5), then x = 2, y = 4, then x+y = 6
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