Multiplying a 2-digit number by 18

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

   Example:

1. The 2-digit number chosen to multiply by 18 is 28.
2. 28 x 2 = 56 (multiply by 2).
3. Add one zero: 560.
4. Subtract: 560 - 56 = 504.
5. So 18 x 28 = 504.

   See the pattern?

1. If the number to be multiplied by 18 is 46:
2. 2 x 46 = 92 (multiply by 2).
   (Think (40 x 2) + (6 x 2) = 80 + 12 = 92)
3. Add one zero: 920.
4. Subtract: 920 - 92 = 828
   (Subtract in easy increments:
   920 - 100 = 820, 820 + 8 = 828)
5. So 46 x 18 = 828.

Practice this procedure, especially selecting the easiest ways to subtract.