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odd/even

by mehrasa » Wed Nov 30, 2011 9:02 am
Is the product abcd even?

1.a^2+b^2+c^2+d^2=0
2. a = b = c = d

[spoiler]OA: A[/spoiler]
but to me the answer is D
stat 2 is sufficient, bcuz it says all numbers are equal
if they r even product is even
if then are all odd, since all are equal it is like 4*X which will be even
what do u think?
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Source: — Data Sufficiency |
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by shankar.ashwin » Wed Nov 30, 2011 9:12 am
Statement 2:

a=b=c=d=1

a*b*c*d = 1 (odd) [abcd not equals 4a, a+a+a+a = 4a] think you mixed up the signs
mehrasa wrote:Is the product abcd even?

1.a^2+b^2+c^2+d^2=0
2. a = b = c = d

[spoiler]OA: A[/spoiler]
but to me the answer is D
stat 2 is sufficient, bcuz it says all numbers are equal
if they r even product is even
if then are all odd, since all are equal it is like 4*X which will be even
what do u think?
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by rijul007 » Wed Nov 30, 2011 9:14 am
mehrasa wrote:Is the product abcd even?


a = b = c = d

stat 2 is sufficient, bcuz it says all numbers are equal
if they r even product is even
if then are all odd, since all are equal it is like 4*X which will be even
what do u think?
If a=b=c=d

a*b*c*d = a^4
We dont know if a is even or odd....
Hence this statement will be Insufficient
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by GMATGuruNY » Wed Nov 30, 2011 9:30 am
mehrasa wrote:Is the product abcd even?

1.a^2+b^2+c^2+d^2=0
2. a = b = c = d

[spoiler]OA: A[/spoiler]
but to me the answer is D
stat 2 is sufficient, bcuz it says all numbers are equal
if they r even product is even
if then are all odd, since all are equal it is like 4*X which will be even
what do u think?
Statement 1: a² + b² + c² + d² = 0.
Since the square of a number can never be negative, the only way to satisfy statement 1 is if a=b=c=d=0.
Thus, abcd = 0, which is even.
SUFFICIENT.

Statement 2: a=b=c=d.
If a=b=c=d=0, then abcd= 0*0*0*0 = 0, which is even.
If a=b=c=d=1, then abcd= 1*1*1*1 = 1, which is not even.
INSUFFICIENT.

The correct answer is A.

The following statement is incorrect:
if then are all odd, since all are equal it is like 4*X which will be even.
a=b=c=d means that abcd = a*a*a*a = a�.
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by chieftang » Thu Dec 01, 2011 4:21 pm
mehrasa wrote:Is the product abcd even?

1.a^2+b^2+c^2+d^2=0
2. a = b = c = d

[spoiler]OA: A[/spoiler]
but to me the answer is D
stat 2 is sufficient, bcuz it says all numbers are equal
if they r even product is even
if then are all odd, since all are equal it is like 4*X which will be even
what do u think?
A

For case 2, 1*1*1*1 = odd.
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