# How to find the derivative of a square root

Many mathematical operations have an inverse, or opposite, operation. Subtraction is the opposite of addition, division is the inverse of multiplication, and so on. Squaring, which we learned about in a previous lesson (exponents ), has an inverse too, called "finding the square root." Remember, the square of a number is that number times itself. The perfect squares are the squares of the whole numbers: 1, 4, 9, 16, 25, 36, 49, 64, 81, 100 …

The square root of a number, n, written

is the number that gives n when multiplied by itself. For example,

because 10 x 10 = 100*Examples*

Here are the square roots of all the perfect squares from 1 to 100.

**Finding square roots of of numbers that aren't perfect squares without a calculator**

1. Estimate - first, get

as close as you can by finding two perfect square roots your number is between.

2. Divide - divide your number by one of those square roots.

3. Average - take the average of the result of step 2 and the root.

4. Use the result of step 3 to repeat steps 2 and 3 until you have a number that is accurate enough for you.

**Example: Calculate the square root of 10 (**

**) to 2 decimal places.**

**1.** Find the two perfect square numbers it lies between.

Solution:

3 2 = 9 and 4 2 = 16, so

lies between 3 and 4.**2.** Divide 10 by 3. 10/3 = 3.33 (you can round off your answer)

**3.** Average 3.33 and 3. (3.33 + 3)/2 = 3.1667

**Repeat step 2:** 10/3.1667 = 3.1579

Category: Bank

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