81

Put a decimal point to the right of the 1 (6561.) Now go 2 numbers to the left. That is the second pair of numbers. Now go 2 more numbers to the left. That is the first pair of numbers. What is the number that is the closest to the square root of 85 without going over 65? That is the first number in your answer. Square that number and subtract from 65. Also mark that number down to the left. Now double it and add a space (XX_). Bring down you second pair of numbers so that you have Y61. How many times does XX_ go into Y61? That is the second number to your answer. Also put that number in the space in XX_. Multiply XX_ by thle second number of your answer and if it matches Y61 you have your answer.