1. Choose a number in the 200s (practice with numbers under 210, then progress to larger ones).
2. The first digit of the square is 4: 4 _ _ _ _
3. The next two digits will be 4 times the last 2 digits: _ X X _ _
4. The last two places will be the square of the last digit: _ _ _ X X

   Example:

1. If the number to be squared is 206:
2. The first digit is 4: 4 _ _ _ _
3. The next two digits are 4 times the last digit:
   4 × 6 = 24: _ 2 4 _ _
4. Square the last digit: 6 × 6 = 36: _ _ _ 3 6
5. So 206 × 206 = 42436.

For larger numbers work right to left:
1. Square the last two digits (keep the carry): _ _ _ X X
2. 4 times the last two digits + carry: _ X X _ _
3. Square the first digit + carry: X _ _ _ _

   See the pattern?

1. If the number to be squared is 225:
2. Square last two digits (keep carry):
   25x25 = 625 (keep 6): _ _ _ 2 5
3. 4 times the last two digits + carry:
   4x25 = 100; 100+6 = 106 (keep 1): _ 0 6 _ _
4. Square the first digit + carry:
   2x2 = 4; 4+1 = 5: 5 _ _ _ _
5. So 225 × 225 = 50625.