ACT Math : Simplifying Square Roots

Study concepts, example questions & explanations for ACT Math

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Example Questions

Example Question #1 : Simplifying Square Roots

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

Possible Answers:

\displaystyle 5\sqrt{3}

\displaystyle 9

\displaystyle 7.5\sqrt{10}

\displaystyle 3\sqrt{5}

Correct answer:

\displaystyle 5\sqrt{3}

Explanation:

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

Example Question #1 : Exponents And Roots

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

Possible Answers:

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

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

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

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

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

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 #22 : Arithmetic

What is \displaystyle \sqrt{50}?

Possible Answers:

\displaystyle 5

\displaystyle 2\sqrt{5}

\displaystyle 10

\displaystyle 5\sqrt{2}

\displaystyle 10\sqrt{2}

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 #1 : Exponents And 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} -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} + \sqrt{6}}{3x - 2}\displaystyle \frac{3x^{2} + \sqrt{6}}{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 #1 : Properties Of Roots And Exponents

Which of the following is the most simplified form of:

\displaystyle \sqrt{468}

 

Possible Answers:

\displaystyle \sqrt{468}

\displaystyle 6\sqrt{13}

\displaystyle 17\sqrt{2}

\displaystyle 4\sqrt{29}

\displaystyle 2\sqrt{117}

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}

Example Question #41 : Basic Squaring / Square Roots

What is \displaystyle \sqrt{432} equal to?

Possible Answers:

\displaystyle 12\sqrt{3}

\displaystyle 6\sqrt{4}

\displaystyle 6\sqrt{3}

\displaystyle 144\sqrt{3}

\displaystyle 12\sqrt{12}

Correct answer:

\displaystyle 12\sqrt{3}

Explanation:

\displaystyle \sqrt{432}

 

1. We know that \displaystyle 432=(144)(3), which we can separate under the square root:

\displaystyle \sqrt{144\cdot 3}

 

2. 144 can be taken out since it is a perfect square: \displaystyle 12\cdot12=144. This leaves us with:

\displaystyle 12\sqrt{3}

This cannot be simplified any further.

Example Question #7 : Simplifying Square Roots

Which of the following is equal to \displaystyle \small \sqrt{420}?

Possible Answers:

\displaystyle \small 28\sqrt{5}

\displaystyle \small 4\sqrt{35}

\displaystyle \small \small 3\sqrt{70}

\displaystyle \small 2\sqrt{105}

\displaystyle \small 6\sqrt{35}

Correct answer:

\displaystyle \small 2\sqrt{105}

Explanation:

When simplifying square roots, begin by prime factoring the number in question. For \displaystyle \small 420, this is:

\displaystyle \small 420 = 2*2*3*5*7

Now, for each pair of numbers, you can remove that number from the square root. Thus, you can say:

\displaystyle \small \small \sqrt{420}=2\sqrt{105}

Another way to think of this is to rewrite \displaystyle \small \small \sqrt{420} as \displaystyle \small \sqrt{4}*\sqrt{105}. This can be simplified in the same manner.

Example Question #8 : Simplifying Square Roots

Which of the following is equivalent to \displaystyle \small \sqrt{700700}?

Possible Answers:

\displaystyle \small 70\sqrt{143}

\displaystyle \small 121\sqrt{7}

\displaystyle \small 770\sqrt{13}

\displaystyle \small 90\sqrt{11}

\displaystyle \small 100\sqrt{77}

Correct answer:

\displaystyle \small 70\sqrt{143}

Explanation:

When simplifying square roots, begin by prime factoring the number in question. This is a bit harder for \displaystyle \small 700700. Start by dividing out \displaystyle \small 100:

\displaystyle \small 700700 = 7007 * 100

Now, \displaystyle \small 7007 is divisible by \displaystyle 7, so:

\displaystyle \small \small 700700 =1001 * 7 * 2*2*5*5

\displaystyle \small 1001 is a little bit harder, but it is also divisible by \displaystyle \small 7, so:

\displaystyle \small 700700 =143*7 * 7 * 2*2*5*5

With some careful testing, you will see that \displaystyle \small 143 = 11 * 13

Thus, we can say:

\displaystyle \small \small 700700 = 2*2*5*5*7 * 7*11*13

Now, for each pair of numbers, you can remove that number from the square root. Thus, you can say:

\displaystyle \small \small \sqrt{700700} = 2*5*7*\sqrt{143}=70\sqrt{143}

Another way to think of this is to rewrite \displaystyle \small \small \small \sqrt{700700} as \displaystyle \small \sqrt{4} * \sqrt{25} * \sqrt{49} * \sqrt{143}. This can be simplified in the same manner.

Example Question #9 : Simplifying Square Roots

What is the simplified (reduced) form of \displaystyle \sqrt{96}?

Possible Answers:

\displaystyle 2\sqrt{48}

\displaystyle 4\sqrt{6}

It cannot be simplified further.

\displaystyle 8\sqrt{3}

\displaystyle 2\sqrt{24}

Correct answer:

\displaystyle 4\sqrt{6}

Explanation:

To simplify a square root, you have to factor the number and look for pairs. Whenever there is a pair of factors (for example two twos), you pull one to the outside.

Thus when you factor 96 you get
\displaystyle \\ \sqrt{96}=\sqrt{2\cdot 2\cdot 2\cdot2\cdot2\cdot 3}\\ \\=2\cdot 2\sqrt{2\cdot 3}\\ \\=4\sqrt{6}

Example Question #10 : Simplifying Square Roots

Which of the following is equal to \displaystyle \small \sqrt{1260}?

Possible Answers:

\displaystyle \small 10\sqrt{7}

\displaystyle \small 6\sqrt{35}

\displaystyle \small 60\sqrt{7}

\displaystyle \small 30\sqrt{3}

\displaystyle \small 26\sqrt{35}

Correct answer:

\displaystyle \small 6\sqrt{35}

Explanation:

When simplifying square roots, begin by prime factoring the number in question. For \displaystyle \small 1260, this is:

\displaystyle \small 1260=2*2*3*3*5*7

Now, for each pair of numbers, you can remove that number from the square root. Thus, you can say:

\displaystyle \small \sqrt{1260}=2*3*\sqrt{35}=6\sqrt{35}

Another way to think of this is to rewrite \displaystyle \small \sqrt{1260} as \displaystyle \small \sqrt{4}*\sqrt{9}*\sqrt{35}. This can be simplified in the same manner.

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