My square root is 80 the two other square roots next to it are 81 and 72 the numbers for those are 9 for 81 and 8 for 72, obviously 80 is much closer  to 81 than 72 so you can eliminate anything 8.5 and below for the square root. It would either be 6, 7, 8, or 9 it is in the higher end of those numbers so you could assume that it is in the 8 or 9’s doing some multiplication i found out that it is closer to a 9 it can’t be higher than .5 again. So cutting the numbers in half i finally came up with an answer 8.94 is very close to the correct square root. I hope this helped you out if you have anything to ask, comment!