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if X^2=y+5 , y=z-2 , z=2x Is x^3 + y^2 +z divisible by 7 a) [#permalink]
02 May 2007, 16:37

if X^2=y+5 , y=z-2 , z=2x
Is x^3 + y^2 +z divisible by 7

a) x>0
b) y=4

Statement (1) ALONE is sufficient, but Statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but Statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient

(1) For x>0 there are infinite (integer) values of the expression above. Doing some calculations we have that, for x=1, A=19; x=2, A=13; x=3, A=49. So The expression could or could not be divisible by 7. Insuff =) B, C or E.

(2) y=4 =) x=3 =) The expression is divisible by 7. Suff =) B.

One thing to point out (and that I forgot to apply in this problem) is the need to start with the easiest looking btw (1) and (2). In this case, it was (2). Doing this could surely help save some precious time on exam day.

saurabhmalpani wrote:

if X^2=y+5 , y=z-2 , z=2x Is x^3 + y^2 +z divisible by 7

(1) x>0 (2) y=4

Statement (1) ALONE is sufficient, but Statement (2) alone is not sufficient. Statement (2) ALONE is sufficient, but Statement (1) alone is not sufficient. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient. EACH statement ALONE is sufficient. Statements (1) and (2) TOGETHER are NOT sufficient

(1) For x>0 there are infinite (integer) values of the expression above. Doing some calculations we have that, for x=1, A=19; x=2, A=13; x=3, A=49. So The expression could or could not be divisible by 7. Insuff =) B, C or E.

(2) y=4 =) x=3 =) The expression is divisible by 7. Suff =) B.

One thing to point out (and that I forgot to apply in this problem) is the need to start with the easiest looking btw (1) and (2). In this case, it was (2). Doing this could surely help save some precious time on exam day.

saurabhmalpani wrote:

if X^2=y+5 , y=z-2 , z=2x Is x^3 + y^2 +z divisible by 7

(1) x>0 (2) y=4

Statement (1) ALONE is sufficient, but Statement (2) alone is not sufficient. Statement (2) ALONE is sufficient, but Statement (1) alone is not sufficient. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient. EACH statement ALONE is sufficient. Statements (1) and (2) TOGETHER are NOT sufficient