Multiplying two 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 × 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 × 27 = 1134.