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Square Root: Definition and Example

Math Glossary: Numbers – Mathbot, the Math Made Easy robot coach

Definition: The square root of a number is a value that, when multiplied by itself, gives that number, written with the radical symbol.

Grade 8

What is a square root?

If s times s equals n, then s is a square root of n. Since 13 x 13 = 169, the square root of 169 is 13. Every positive number has two square roots, one positive and one negative, but the radical symbol means the positive one.

What are perfect squares?

Numbers like 1, 4, 9, 16, 25, 36, 49, 64, 81, 100, 121, 144. Their square roots are whole numbers.

How do you estimate others?

Find the neighboring perfect squares. For the square root of 83, use 81 and 100. So it is just above 9. Since 9.1 squared is 82.81, the answer is about 9.11.

How do you solve with it?

If x2 = 196, then x = 14 or x = -14. The side of a square garden with area 196 square feet is 14 feet.

What are the common mistakes?

Halving the number instead of taking the root: the square root of 36 is 6, not 18. Another is claiming the root of a negative number is real. In the real numbers, the square root of -9 does not exist.

Example: The square root of 225 is 15, because 15 x 15 = 225.

Where to learn it

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