What is a number you can square bigger than 800 but smaller than 900?

A number you can square that is bigger than 800 but smaller than 900 is 30. When you square 30, you get 900, which is on the upper limit. However, if you want a number that fits strictly between those limits, 29.5 is a suitable choice, as squaring it gives 870.25, which is between 800 and 900.