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n=?

by Max@Math Revolution » Thu Aug 04, 2016 3:50 am
n=?
1) n^2=1
2) n^3=1

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Source: — Data Sufficiency |

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by Brent@GMATPrepNow » Thu Aug 04, 2016 7:05 am
Max@Math Revolution wrote: n = ?

1) n² = 1
2) n³ = 1
Target question: What is the value of n?

Statement 1: n² = 1
There are TWO possible solutions to this equation.
EITHER n = 1 OR n = -1
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: n³ = 1
There's only ONE solution: n = 1
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer = B

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Brent
Brent Hanneson - Creator of GMATPrepNow.com
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by Max@Math Revolution » Sun Aug 07, 2016 4:47 pm
In the original condition, there is 1 variable (n) and there is a high chance that D is the correct answer.
In condition 1), we get n=-1 and 1. The answer is not unique and the condition is not sufficient.
In condition 2), we only have n=1. The answer is not unique and the condition is sufficient. Hence, the correct answer is B.

- Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.
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