I estimated that the square root of 79 is 8.9. First of all I found the perfects squares above and below 79. 64 is the perfect square before 79 and 81 is the perfect square after 79.   8*8 is 64 and 9*9 is 81. To get the mid way point between these numbers I got the midway point of 8 and 9 and its 8.5. So i added 8.5 to 64 and got 72.5. So 72.5 is the midway point. 79 is closer to 81 then to 72.5 so the number will be higher than 5. So it has to be 8.6, 8.7, 8.8, or 8.9. So now I started to eliminate numbers, I eliminated 8.6 and 8.7 because 79 is only two spaces away from 81 so it has to be a higher number. So now I typed it in the calculator and got 8.88 so I rounded it to 8.9. The the square root of 79 is about 8.9.