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kartikshah
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Does x + y = x.y ?kartikshah wrote:Does x + y = x.y ?
(1) The product of x and positive integer z is not x.
(2) y is neither positive nor negative.
Why is B alone not sufficient? OA is C
Source: Master GMAT
(1) The product of x and positive integer z is not x.
If xz=x => (z-1)x = 0. Either z=1 OR x=0. If this is NOT true, then we have z is not equal to 1 AND x is not equal to 0. If x is not 0,
2+2 = 2*2, the expression is true.
2+1 does not equal 2*1, expression isn't true. Insufficient.
(2) y is neither positive nor negative.
If y is neither positive nor negative, y=0.
If the expression is true, x+0 =0.x => x=0. So expression is true when x=0
If x is not equal to 0, expression is not true.
Since we don't know whether x equals 0 or not, this statement is insufficient.
Together, we have:
y=0, x is not zero.
Therefore, x+y is not equal to x.y. Sufficiently answered as NO.
Hence C is the correct answer.
Let me know if this helps
