GRE Math : How to simplify square roots

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #1 : How To Simplify Square Roots

Simplify the following: (√(6) + √(3)) / √(3)

Possible Answers:

3√(2)

√(3)

1

√(2) + 1

None of the other answers

Correct answer:

√(2) + 1

Explanation:

Begin by multiplying top and bottom by √(3):

(√(18) + √(9)) / 3

Note the following:

√(9) = 3

√(18) = √(9 * 2) = √(9) * √(2) = 3 * √(2)

Therefore, the numerator is: 3 * √(2) + 3.  Factor out the common 3: 3 * (√(2) + 1)

Rewrite the whole fraction:

(3 * (√(2) + 1)) / 3

Simplfy by dividing cancelling the 3 common to numerator and denominator: √(2) + 1

Example Question #2 : How To Simplify Square Roots

what is 

√0.0000490

Possible Answers:

0.00007

49

0.007

7

0.07

Correct answer:

0.007

Explanation:

easiest way to simplify: turn into scientific notation

√0.0000490= √4.9 X 10-5

finding the square root of an even exponent is easy, and 49 is  a perfect square, so we can write out an improper scientific notation:

√4.9 X 10-5√49 X 10-6

√49 = 7; √10-6 = 10-3 this is equivalent to raising 10-6 to the 1/2 power, in which case all that needs to be done is multiply the two exponents: 7 X 10-3= 0.007

Example Question #3 : How To Simplify Square Roots

Simplify: \(\displaystyle \sqrt{576}\)

Possible Answers:

\(\displaystyle 10\sqrt{12}\)

\(\displaystyle 24\)

\(\displaystyle 12\sqrt{3}\)

\(\displaystyle 12\sqrt{6}\)

\(\displaystyle 34\)

Correct answer:

\(\displaystyle 24\)

Explanation:

In order to take the square root, divide 576 by 2.

\(\displaystyle \dpi{100} \sqrt{576}= \sqrt{2}\sqrt{288}=\sqrt{2}\sqrt{2}\sqrt{144}=\sqrt{4}\sqrt{144}=2\cdot 12=24\)

Example Question #4 : How To Simplify Square Roots

Simplify (\frac{16}{81})^{1/4}\(\displaystyle (\frac{16}{81})^{1/4}\).

Possible Answers:

\frac{2}{3}\(\displaystyle \frac{2}{3}\)

\frac{4}{9}\(\displaystyle \frac{4}{9}\)

\frac{2}{81}\(\displaystyle \frac{2}{81}\)

\frac{8}{81}\(\displaystyle \frac{8}{81}\)

\frac{4}{81}\(\displaystyle \frac{4}{81}\)

Correct answer:

\frac{2}{3}\(\displaystyle \frac{2}{3}\)

Explanation:

(\frac{16}{81})^{1/4}\(\displaystyle (\frac{16}{81})^{1/4}\)

\(\displaystyle =\)\frac{16^{1/4}}{81^{1/4}}\(\displaystyle \frac{16^{1/4}}{81^{1/4}}\)

\(\displaystyle =\)\frac{(2\cdot 2\cdot 2\cdot 2)^{1/4}}{(3\cdot 3\cdot 3\cdot 3)^{1/4}}\(\displaystyle \frac{(2\cdot 2\cdot 2\cdot 2)^{1/4}}{(3\cdot 3\cdot 3\cdot 3)^{1/4}}\)

\(\displaystyle =\)\frac{2}{3}\(\displaystyle \frac{2}{3}\)

Example Question #22 : Arithmetic

Simplfy the following radical \(\displaystyle \sqrt{20x^{2}}\).

Possible Answers:

\(\displaystyle 4\sqrt{5x}\)

\(\displaystyle 2\sqrt{5x^{2}}\)

\(\displaystyle 2x\sqrt{5}\)

\(\displaystyle 2x\sqrt{10}\)

Correct answer:

\(\displaystyle 2x\sqrt{5}\)

Explanation:

You can rewrite the equation as \(\displaystyle \sqrt{20x^2}=(x)\sqrt{5} \cdot \sqrt{4}\).

This simplifies to \(\displaystyle 2x\sqrt{5}\).

Example Question #5 : How To Simplify Square Roots

Which of the following is equal to \(\displaystyle \sqrt{75}\) ?

Possible Answers:

\(\displaystyle 3\sqrt{5}\)

\(\displaystyle 9\)

\(\displaystyle 7.5\sqrt{10}\)

\(\displaystyle 5\sqrt{3}\)

Correct answer:

\(\displaystyle 5\sqrt{3}\)

Explanation:

√75 can be broken down to √25 * √3. Which simplifies to 5√3.

Example Question #12 : How To Simplify Square Roots

Simplify \sqrt{a^{3}b^{4}c^{5}}\(\displaystyle \sqrt{a^{3}b^{4}c^{5}}\).

Possible Answers:

a^{2}bc\sqrt{bc}\(\displaystyle a^{2}bc\sqrt{bc}\)

a^{2}b^{2}c\sqrt{ab}\(\displaystyle a^{2}b^{2}c\sqrt{ab}\)

a^{2}b^{2}c^{2}\sqrt{bc}\(\displaystyle a^{2}b^{2}c^{2}\sqrt{bc}\)

ab^{2}c^{2}\sqrt{ac}\(\displaystyle ab^{2}c^{2}\sqrt{ac}\)

a^{2}bc^{2}\sqrt{ac}\(\displaystyle a^{2}bc^{2}\sqrt{ac}\)

Correct answer:

ab^{2}c^{2}\sqrt{ac}\(\displaystyle ab^{2}c^{2}\sqrt{ac}\)

Explanation:

Rewrite what is under the radical in terms of perfect squares:

x^{2}=x\cdot x\(\displaystyle x^{2}=x\cdot x\)

x^{4}=x^{2}\cdot x^{2}\(\displaystyle x^{4}=x^{2}\cdot x^{2}\)

x^{6}=x^{3}\cdot x^{3}\(\displaystyle x^{6}=x^{3}\cdot x^{3}\)

Therefore, \sqrt{a^{3}b^{4}c^{5}}= \sqrt{a^{2}a^{1}b^{4}c^{4}c^{1}}=ab^{2}c^{2}\sqrt{ac}\(\displaystyle \sqrt{a^{3}b^{4}c^{5}}= \sqrt{a^{2}a^{1}b^{4}c^{4}c^{1}}=ab^{2}c^{2}\sqrt{ac}\).

Example Question #6 : How To Simplify Square Roots

What is \(\displaystyle \sqrt{50}\)?

Possible Answers:

\(\displaystyle 5\sqrt{2}\)

\(\displaystyle 10\sqrt{2}\)

\(\displaystyle 5\)

\(\displaystyle 10\)

\(\displaystyle 2\sqrt{5}\)

Correct answer:

\(\displaystyle 5\sqrt{2}\)

Explanation:

We know that 25 is a factor of 50. The square root of 25 is 5. That leaves \(\displaystyle \sqrt{2}\) which can not be simplified further.

Example Question #13 : How To Simplify Square Roots

Which of the following is equivalent to \frac{x + \sqrt{3}}{3x + \sqrt{2}}\(\displaystyle \frac{x + \sqrt{3}}{3x + \sqrt{2}}\)?

Possible Answers:

\frac{3x^{2} + \sqrt{6}}{3x - 2}\(\displaystyle \frac{3x^{2} + \sqrt{6}}{3x - 2}\)

\frac{3x^{2} -x \sqrt{2} + 3x\sqrt{3} - \sqrt{6}}{9x^{2} - 2}\(\displaystyle \frac{3x^{2} -x \sqrt{2} + 3x\sqrt{3} - \sqrt{6}}{9x^{2} - 2}\)

\frac{4x + \sqrt{5}}{3x + 2}\(\displaystyle \frac{4x + \sqrt{5}}{3x + 2}\)

\frac{3x^{2} + 3x\sqrt{2} + x\sqrt{3} +\sqrt{6}}{9x^{2} - 2}\(\displaystyle \frac{3x^{2} + 3x\sqrt{2} + x\sqrt{3} +\sqrt{6}}{9x^{2} - 2}\)

\frac{3x^{2} - \sqrt{6}}{9x^{2} + 2}\(\displaystyle \frac{3x^{2} - \sqrt{6}}{9x^{2} + 2}\)

Correct answer:

\frac{3x^{2} -x \sqrt{2} + 3x\sqrt{3} - \sqrt{6}}{9x^{2} - 2}\(\displaystyle \frac{3x^{2} -x \sqrt{2} + 3x\sqrt{3} - \sqrt{6}}{9x^{2} - 2}\)

Explanation:

Multiply by the conjugate and the use the formula for the difference of two squares:

\frac{x + \sqrt{3}}{3x + \sqrt{2}}\(\displaystyle \frac{x + \sqrt{3}}{3x + \sqrt{2}}\)

\(\displaystyle =\) \frac{x + \sqrt{3}}{3x + \sqrt{2}}\cdot \frac{3x - \sqrt{2}}{3x - \sqrt{2}}\(\displaystyle \frac{x + \sqrt{3}}{3x + \sqrt{2}}\cdot \frac{3x - \sqrt{2}}{3x - \sqrt{2}}\)

\(\displaystyle =\) \frac{3x^{2} -x \sqrt{2} + 3x\sqrt{3} - \sqrt{6}}{(3x)^{2} - (\sqrt{2})^{2}}\(\displaystyle \frac{3x^{2} -x \sqrt{2} + 3x\sqrt{3} - \sqrt{6}}{(3x)^{2} - (\sqrt{2})^{2}}\) 

\(\displaystyle =\) \frac{3x^{2} -x \sqrt{2} + 3x\sqrt{3} - \sqrt{6}}{9x^{2} - 2}\(\displaystyle \frac{3x^{2} -x \sqrt{2} + 3x\sqrt{3} - \sqrt{6}}{9x^{2} - 2}\)

Example Question #14 : How To Simplify Square Roots

Which of the following is the most simplified form of:

\(\displaystyle \sqrt{468}\)

 

Possible Answers:

\(\displaystyle 2\sqrt{117}\)

\(\displaystyle 6\sqrt{13}\)

\(\displaystyle 17\sqrt{2}\)

\(\displaystyle \sqrt{468}\)

\(\displaystyle 4\sqrt{29}\)

Correct answer:

\(\displaystyle 6\sqrt{13}\)

Explanation:

First find all of the prime factors of \(\displaystyle 468\)

\(\displaystyle 468=6\ast78=6\ast6\ast13=2\ast3\ast2\ast3\ast13\)

So \(\displaystyle \sqrt{468}=\sqrt{2\ast2\ast3\ast3\ast13}=2\ast3\sqrt{13}=6\sqrt{13}\)

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