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Two digit number


gmat20034

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x is the tens digit

y is the unit digit

we're looking for a

 

a = 10x + y

 

y/x = 2/3 leads to y = 2x/3

y*x = 54 leads to 2xx/3 = 54

 

x^2 = 81 leads to x = 9 or x = -9

that means y = 6 or y = -6

 

which gives a = 96 or a = -96

 

I would argue that in -96 the tens digit is -9 and the unit digit is -6. Alternatively, I would say it is a negative number with 9 and six as digits. So the ratio is preserved. Do I miss a mathematical rule here?

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