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number system

by dream700 » Wed Feb 10, 2010 4:34 am
What is the value of (x - y)^4?
(1) The product of x and y is 7.
(2) x and y are integers.

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

The OA is C

I don't know hoe from product of x and y we will be getting the value. Am I missing something here or it's just that OA is wrong?

Regards,
Dream700
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Source: — Data Sufficiency |
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by thephoenix » Wed Feb 10, 2010 5:10 am
OA is correct

for s1) if x=7/2 and y=2 prod=7 and exp=81/16
if x=7 and y=1 prod=7 and exp=6^4
insuff

for s2) x can be any int and y can be any int and exp can have any value insuff

togather

x can be 7 or 1 respective value of y can be 1 or 7
in bth the case prod=7 and exp=6^4
hence suff
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by ajith » Wed Feb 10, 2010 9:45 am
dream700 wrote:What is the value of (x - y)^4?
(1) The product of x and y is 7.
(2) x and y are integers.
1) Product of x and y is 7 is not sufficient - (x, y )can be (3.5,2) or (1,7) or similar...
2) x and y are integers are not sufficient (x, y )can be (3,2) or (6,7) or similar...

Combined (x,y) can be either (1,7) or (7,1)
but in either case (x - y)^4? = 6^4 =( -6)^4
C
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by sanju09 » Thu Feb 11, 2010 12:00 am
dream700 wrote:What is the value of (x - y)^4?
(1) The product of x and y is 7.
(2) x and y are integers.

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

The OA is C

I don't know hoe from product of x and y we will be getting the value. Am I missing something here or it's just that OA is wrong?

Regards,
Dream700
Let's start with checking for [spoiler]C[/spoiler] itself as each statement alone is no doubt insufficient.

If product of two integers is prime then one is 1 and the other is the prime, and 1 less than the prime raised to power 4 can be uniquely answered.

[spoiler]Hence, C[/spoiler]
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