Re: If x is an integer, does 2x have twice as many factors as x does? 1)
[#permalink]
Updated on: 30 Oct 2021, 10:55
UPDATED 10.17
Statement 1 -- Sufficient.
X to the power of y is divisible by 2. For any number to be a multiple of 2, it must be even. And if Y is an integer, X to the power of Y would need to be an even perfect square. X could be positive or negative since any number squared is positive. So test cases for X could be positive or negative.
Some possible values for x and 2x are...
x=-4, -2, 0, 2, 4, 6, 8
2x=-8, -4, 0, 4, 8, 12, 16
If X is -4, X has 5 factors--1, -1, -2, 2, 4, -4--and 2x has 8 factors -- 1, -1, 2, -2, 4, -4, 8, -8. Answer is no, not double.
If X is 0, X has one factor--0--and 2x equals 0, which also has 1 factor. Answer is no, not double.
If X is 4, X has 3 factors--1, 2, 4--and 2X has 4 factors--1, 2, 4, 8. Again, answer is no, not double.
No matter what permissible value of X, 2X never has double the number of factors that X has. Statement 1 is sufficient.
Statement 2 -- Insufficient.
"x/y is even" tells us a few things about x. X could be even, and that would yield the same 'no' as above. But, for this statement, we don't know anything about Y to suggest it must be an integer, so X could also be odd, which can violate this statement. For example, if x/y is 6, X could be 3 and Y could be 1/2. 3 (X) has two factors--1, 3--whereas 6 (2x) has 4 factors--1, 2, 3, 6. This yields a "yes". X could be 4 and Y could be 2, making the answer to the question stem "no", because 2x has 3 factors whereas X has 2 factors. So, statement 2 is insufficient.
The correct answer is A.
Originally posted by
xvibrant on 16 Oct 2021, 10:32.
Last edited by
xvibrant on 30 Oct 2021, 10:55, edited 5 times in total.