Multiplying a 2-digit number by 27

1. Select a 2-digit number .
2. Multiply it by 3.
3. Add one zero.
4. Subtract the number obtained by multiplying by 3 from the last number.

   Example:

1. The 2-digit number chosen to multiply by 27 is 42.
2. 3 x 42 = 120 + 6 = 126 (multiply by 3).
3. Subtract left to right in steps:
   1260 - 100 - 20 - 6 = 1160 - 20 - 6 = 1140 - 6 = 1134
   or 1260 - 130 + 4 - 1130 + 4 = 1134.
4. So 42 x 27 = 1134.

   See the pattern?

1. If the number to be multiplied by 27 is 63:
2. 3 x 63 = 189 (multiply by 3).
3. Add one zero: 1890.
4. Subtract: 1890 - 189 = 1701
   (Subtract left to right in steps:
   1890 - 189 = 1890 - 100 - 80 - 9 = 1790 - 80 - 9 = 1710 - 9 = 1701
   or 1890 - 190 + 1 = 1700 + 1 = 1701.
5. So 63 x 27 = 1701.