Suppose you want to evaluate something like on your calculator. First enter the number 25.85. Then hit the square root key. The resulting answer should be something like 5.084289528. Keep in mind that this is not really the exact answer.
Calculators are limited to a specific number of decimal places.
My scientific calculator can display no more than 10 places. However, for most purposes, 5.084289528 is a fine approximation for . Now suppose you want to evaluate something like on your calculator. You will then need to hit the equal sign. Do NOT hit the square root key until after you hit the equal sign.