Explanation

A square root is equivalent to the power, so the expression we are given is equivalent to



It's often a good idea to convert a square root into an exponent of power 1/2, because then you can use exponent rules. Such as now: exponents of exponents multiply, so we have



We can write the inside of the parentheses as



If these rules are foreign to you, you may want to consult the GMAT Free Math Review. Since the two terms inside the parenthesis are multiplied, we can distribute the exponent:



The left factor is now the fourth root of 81, which is the square root of the square root of 81, which is the square root of 9, which is 3. In the right factor, we once again multiply exponents:



We have our answer: choice (E). This question can be solved less formally, but just as exactly, by starting with the inside of the radical with the following reasoning. The square root of 81 is 9, and there are 4 decimal places inside the radical, so expression is equal to 0.09 to the power 1/2. Using that same reasoning again, we can see that the answer must be 0.3. The correct answer is (E).