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if x and y are prime, is xy odd ? 1... x - y is even. [#permalink]
12 Nov 2006, 08:39

00:00

A

B

C

D

E

Difficulty:

5% (low)

Question Stats:

0% (00:00) correct
0% (00:00) wrong based on 0 sessions

if x and y are prime, is xy odd ?

1... x − y is even.
2... x / y is not an integer.

Ο only statement 1 is sufficient to answer the question.
Ο only statement 2 is sufficient to answer the question.
Ο neither statement is sufficient, but together, they are.
Ο statement 1 is very sufficient...and so is statement 2.
Ο no can do.

Ο only statement 1 is sufficient to answer the question.
Ο only statement 2 is sufficient to answer the question.
Ο neither statement is sufficient, but together, they are.
Ο statement 1 is very sufficient...and so is statement 2.
Ο no can do.

1) We know that X and Y are prime and there is only 1 even prime. For X-Y to be even both X and Y must be ODD (Cannot have ODD - EVEN to equal EVEN). This means XY will always be ODD. SUFF

2) Only tells us that Y does not go into X or that X < Y but does not tell us anything that will help in answering this questions.

for xy to be odd thus all we need to proof is x,y not = 2

x-y is even

thus both are odd OR BOTH ARE TWO ........INSUFF

x/y is not an intiger

either ways any prime is not devisible except by itself and one so deviding any two primes will always yield a non integer ( this includes 2 too)...insuff

Ο only statement 1 is sufficient to answer the question. Ο only statement 2 is sufficient to answer the question. Ο neither statement is sufficient, but together, they are. Ο statement 1 is very sufficient...and so is statement 2. Ο no can do.

I will take E

1) say x=5 y=3 product is even though their diff is even
say x=7 y=3 product is odd though their diff is even
So A not suff

St1:
We know both x and y must be odd primes. So xy is odd. Sufficient.

St2:
Insufficient. 2/7, 3/5 are all non-integers but the first pair (2 and 7) will yield an even product while the second pair (3 and 5) will yield an odd product.

St1: We know both x and y must be odd primes. So xy is odd. Sufficient.

St2: Insufficient. 2/7, 3/5 are all non-integers but the first pair (2 and 7) will yield an even product while the second pair (3 and 5) will yield an odd product.