Repeated subtraction is taking a number and subtracting by increasing odd numbers. The number of steps it takes is the sq root of the number.
So you take the number, subtract 1. Take that answer and subtract 3. Take THAT answer and subtract 5.... Repeat until you get to 0. Count the "steps" and that's the square root of the number.
To find: √81
The steps to find the square root of 81 is:
Step 1. 81 – 1 = 80
Step 2. 80 – 3 = 77
Step 3. 77 – 5 = 72
Step 4. 72 – 7 = 65
Step 5. 65 – 9 = 56
Step 6. 56 – 11 = 45
Step 7. 45 – 13 = 32
Step 8. 32 – 15 = 17
Step 9. 17 – 17 = 0
Here, the result “0” is obtained in step 9. So the square root of 81, √81 is 9.