What is the square root of x?

[aaron1981]

What is the square root of x?

1) The cube root of x is 81.
2) The 6th root of x is 9.

Pl. help me with this confusing question.

[soudeh]

The first data is usable because it helps to find the number ,since it is odd root

Other information is talking about 6th root ( which is even)
So your original number could be negative or positive

All in all, the answer is A

[aaron1981]

The first data is usable because it helps to find the number ,since it is odd root

Other information is talking about 6th root ( which is even)
So your original number could be negative or positive

All in all, the answer is A

I think the second one is also usable since '9' is positive and its a root of a number, so the base number should be positive.

Experts, need help...

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Hi aaron1981,

This question is a 'lift' of an OG question:
GMAT2017: pg. 276, Q240
GMAT2018: pg. 272, Q240

When dealing with this type of math, you have to be clear on the difference between:
X^2 = 9 ... this has two solutions: +3 and -3
(root9) ... this has one solution: +3

When a question asks for the square root of a number, there's only one answer: the POSITIVE one. In this question, both of the Facts give you enough information to determine the value of X, so you could then determine the square root of X. Thus, both Facts are SUFFICIENT

Final Answer: D

GMAT assassins aren't born, they're made,
Rich

[Jeff@TargetTestPrep]

What is the square root of x?

1) The cube root of x is 81.
2) The 6th root of x is 9.

Statement One Alone:

The cube root of x is 81

We can create the equation:

∛x = 81

x = 81^3 = 3^12, so the square root of x is 3^6.

Statement one alone is sufficient to answer the question.

Statement Two Alone:

The 6th root of x is 9.

We can create the equation:

^6√x = 9

x = 9^6 = 3^12

So the square root of x is 3^6.

Answer: D