If you do not have a calculator, you can estimate a decimal approximation of the square root of a number. Here is how, using an example. Suppose you want to know the square root of 20.

You can start out by noting that since √16 = 4 and √25 = 5, then √20 must be between 4 and 5.

Let's say for example that it is 4.5. Square 4.5, and see if the result is over or under 20, and improve your guess based on that. Repeat this process until you have the desired accuracy (amount of decimals). This is a very simple process and can done by any students!