When you go to a  grocery store, you can use square roots. If you only have 90 dollars and you go to the store you need to know how may things you can get. You are walking through the rows and your kids are begging for this and that but you need 9 boxes of cake mix for 9 dollars it equals 81 dollars then you add tax 85.46. On a calculator you do 2nd x squared then 85.46 and you get the price for one box and you see if any are cheaper then that. If not you know you have a little money left over and can get your kids something.