If you can use a calculator, simply ask for the square root of 22 and you will be given something like this (depending on the number of digits the calculator can hold):
[tex] \sqrt(22) = 4.69041575982 [/tex]
We want to round it to four decimal places, so we only want four digits after the decimal separator. Our only doubt will be on the fourth decimal digit.
So, we must choose between
[tex] \sqrt(22) \approx 4.6904 \text{ and } \sqrt(22) \approx 4.6905 [/tex]
To make this decision, we need the next decimal digit, i.e. the fifth, which is 1. If the fifth digit is 0,1,2,3 or 4, which is the case, we round down, so the answer is 4.6904.
If the fifth digits was 5,6,7,8 or 9, we would have rounded up, so the answer would have been 4.6905.
