First you find the perfect square by multiplying two of the same numbers together to get something close to 20 .

The two squares for 20 are 16 and 25 . 

To get 16 we multiplied 4 twice , and for 25 we multiplied 5 twice . 

Make a number line for the numbers in between and the square root of the numbers in between . On the number line find the number 20 and the square root under it . 

The square root for 20 is 4.4 .

I checked it on the calculator and it gave me 4.4 . 

I was correct .