Practice GMAT Data Sufficiency Question
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What is the value of xn – ny – nz?
 x – y – z = 10
 n = 5
Correct Answer: C
 Factor the original equation:
xn – ny – nz = n(x  y  z)  If we know the value of both n and x  y  z, we can determine the value of xn – ny – nz.

Evaluate Statement (1) alone.
 Since x – y – z = 10, based upon the above factoring:
xn – ny – nz = n(10)
However, we do not know the value of n so we cannot solve for the value of xn – ny – nz.  Statement (1) is NOT SUFFICIENT.
 Since x – y – z = 10, based upon the above factoring:

Evaluate Statement (2) alone.
 Since n = 5, based upon the above factoring:
xn – ny – nz = 5(x  y  z)
However, we do not know the value of x  y  z so we cannot solve for the value of xn – ny – nz.  Statement (2) is NOT SUFFICIENT.
 Since n = 5, based upon the above factoring:

Evaluate Statements (1) and (2) together.
 Since n = 5 and x  y  z = 10, based upon the above factoring:
xn – ny – nz = n(x  y  z)=5(10)=50  Statements (1) and (2), when taken together, are SUFFICIENT.
 Since n = 5 and x  y  z = 10, based upon the above factoring:
 Since Statement (1) alone is NOT SUFFICIENT and Statement (2) alone is NOT SUFFICIENT, but Statements (1) and (2), when taken together, are SUFFICIENT, answer C is correct.
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