SAT Math : How to multiply square roots

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #1 : How To Multiply Square Roots

Simplify: \(\displaystyle \sqrt{7}*\sqrt{14}\)

Possible Answers:

\(\displaystyle \sqrt{98}\)

\(\displaystyle 7\sqrt{2}\)

\(\displaystyle 7\sqrt{3}\)

\(\displaystyle 2\sqrt{7}\)

\(\displaystyle \sqrt{21}\)

Correct answer:

\(\displaystyle 7\sqrt{2}\)

Explanation:

When multiplying square roots, you are allowed to multiply the numbers inside the square root. Then simplify if necessary.

\(\displaystyle \sqrt{7}*\sqrt{14}=\sqrt{7*14}=\sqrt{98}=\sqrt{49}*\sqrt{2}=7\sqrt{2}\)

Example Question #1 : How To Multiply Square Roots

Simplify: \(\displaystyle \sqrt{10}*\sqrt{15}\)

Possible Answers:

\(\displaystyle 75\sqrt{2}\)

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

\(\displaystyle 5\sqrt{6}\)

\(\displaystyle \sqrt{150}\)

\(\displaystyle 6\sqrt{5}\)

Correct answer:

\(\displaystyle 5\sqrt{6}\)

Explanation:

When multiplying square roots, you are allowed to multiply the numbers inside the square root. Then simplify if necessary.

\(\displaystyle \sqrt{10}*\sqrt{15}=\sqrt{10*15}=\sqrt{150}=\sqrt{25}*\sqrt{6}=5\sqrt{6}\)

Example Question #1 : Square Roots And Operations

Simplify: \(\displaystyle \sqrt{24}*3\sqrt{8}\)

Possible Answers:

\(\displaystyle 8\sqrt{14}\)

\(\displaystyle 16\sqrt{6}\)

\(\displaystyle 24\sqrt{3}\)

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

\(\displaystyle 24\sqrt{6}\)

Correct answer:

\(\displaystyle 24\sqrt{3}\)

Explanation:

When multiplying square roots, you are allowed to multiply the numbers inside the square root. Then simplify if necessary.

\(\displaystyle \sqrt{24}*3\sqrt{8}=3\sqrt{24*8}=3\sqrt{192}=3\sqrt{64}*\sqrt{3}=24\sqrt{3}\)

Example Question #2 : Square Roots And Operations

Simplify:

\(\displaystyle (\sqrt{3}+\sqrt{5})(\sqrt{2}+\sqrt{6})\)

Possible Answers:

\(\displaystyle \sqrt{6}+\sqrt{18}+\sqrt{10}+\sqrt{30}+8\)

\(\displaystyle \sqrt{18}+\sqrt{10}\)

\(\displaystyle 4\sqrt{6}+5\sqrt{2}+\sqrt{3}\)

\(\displaystyle \sqrt{6}+\sqrt{30}\)

\(\displaystyle \sqrt{6}+3\sqrt{2}+\sqrt{10}+\sqrt{30}\)

Correct answer:

\(\displaystyle \sqrt{6}+3\sqrt{2}+\sqrt{10}+\sqrt{30}\)

Explanation:

To simplify the problem, just distribute the radical to each term in the parentheses. 

\(\displaystyle (\sqrt{3}+\sqrt{5})(\sqrt{2}+\sqrt{6})=\)

\(\displaystyle \sqrt{6}+\sqrt{18}+\sqrt{10}+\sqrt{30}=\)

\(\displaystyle \sqrt{6}+3\sqrt{2}+\sqrt{10}+\sqrt{30}\)

Example Question #1 : How To Multiply Square Roots

Evaluate and simplify: 

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

Possible Answers:

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

\(\displaystyle 20\sqrt{6}\)

\(\displaystyle \sqrt{22}\)

\(\displaystyle 2\sqrt{30}\)

\(\displaystyle 30\sqrt{2}\)

Correct answer:

\(\displaystyle 2\sqrt{30}\)

Explanation:

To multiply square roots, we multiply the numbers inside the radical and we can simplify them if possible.

\(\displaystyle \\ \sqrt{10}*\sqrt{12}\\=\sqrt{10*12}\\=\sqrt{120}\\=\sqrt{4}*\sqrt{30}\\=2\sqrt{30}\)

Example Question #2 : Square Roots And Operations

Simplify and evaluate: 

\(\displaystyle \sqrt{12}*\sqrt{48}\)

Possible Answers:

\(\displaystyle 24\)

\(\displaystyle 8\sqrt{3}\)

\(\displaystyle 18\)

\(\displaystyle 16\sqrt{2}\)

\(\displaystyle 24\sqrt{3}\)

Correct answer:

\(\displaystyle 24\)

Explanation:

To multiply square roots, we multiply the numbers inside the radical and we can simplify them if possible.

In this case, let's simplify each individual radical and multiply them.

\(\displaystyle \\\sqrt{12}*\sqrt{48}\\=\sqrt{4}*\sqrt{3}*\sqrt{16}*\sqrt{3}\\=2\sqrt{3}*4\sqrt{3}\\=8*3=24\)

 

Example Question #1 : How To Multiply Square Roots

Simplify: \(\displaystyle \sqrt{x+5}*\sqrt{x-5}\)

Possible Answers:

\(\displaystyle \sqrt{x^2-25}\)

\(\displaystyle x-5\)

\(\displaystyle x+5\)

\(\displaystyle x^2-25\)

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

Correct answer:

\(\displaystyle \sqrt{x^2-25}\)

Explanation:

To multiply square roots, we multiply the numbers inside the radical and we can simplify them if possible.

\(\displaystyle \\\sqrt{x+5}*\sqrt{x-5}\\=\sqrt{(x+5)(x-5)}\\=\sqrt{x^2-25}\)

Example Question #1 : How To Multiply Square Roots

Simplify: 

\(\displaystyle \sqrt{6}*2\sqrt{3}\)

Possible Answers:

\(\displaystyle 6\sqrt{2}\)

\(\displaystyle 6\sqrt{3}\)

\(\displaystyle 12\sqrt{2}\)

\(\displaystyle 4\sqrt{6}\)

\(\displaystyle 2\sqrt{6}\)

Correct answer:

\(\displaystyle 6\sqrt{2}\)

Explanation:

To multiply square roots, we multiply the numbers inside the radical.

Any numbers outside the radical are also multiplied. We can simplify them if possible.

\(\displaystyle \\\sqrt{6}*2\sqrt{3}\\=2\sqrt{6*3}\\=2\sqrt{18}\\=2\sqrt{9}*\sqrt{2}\\=2*3\sqrt{2}\\=6\sqrt{2}\)

Example Question #3 : How To Multiply Square Roots

Simplify: 

\(\displaystyle 4\sqrt{7}*\sqrt{21}\)

Possible Answers:

\(\displaystyle 3\sqrt{7}\)

\(\displaystyle 11\sqrt{3}\)

\(\displaystyle 12\sqrt{21}\)

\(\displaystyle 28\sqrt{3}\)

\(\displaystyle 7\sqrt{7}\)

Correct answer:

\(\displaystyle 28\sqrt{3}\)

Explanation:

To multiply square roots, we multiply the numbers inside the radical.

Any numbers outside the radical are also multiplied. 

We can simplify them if possible.

\(\displaystyle \\4\sqrt{7}*\sqrt{21}\\ =4\sqrt{7*21}\\=4\sqrt{7*7*3}\\=4*7\sqrt{3}\\=28\sqrt{3}\)

Example Question #1 : How To Multiply Square Roots

Simplify: 

\(\displaystyle 2\sqrt{10}*5\sqrt{20}\)

Possible Answers:

\(\displaystyle 200\)

\(\displaystyle 100\sqrt{2}\)

\(\displaystyle 20\sqrt{5}\)

\(\displaystyle 50\sqrt{2}\)

\(\displaystyle 40\sqrt{10}\)

Correct answer:

\(\displaystyle 100\sqrt{2}\)

Explanation:

To multiply square roots, we multiply the numbers inside the radical.

Any numbers outside the radical are also multiplied. 

We can simplify them if possible.

\(\displaystyle \\2\sqrt{10}*5\sqrt{20}\\=10\sqrt{10*20}\\=10\sqrt{10*10*2}\\=10*10\sqrt{2}\\=100\sqrt{2}\)

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