Multiplying a 2- or 3-digit number by 2 1/2

1. Select a 2- or 3-digit number.
2. Divide by 4 (or by 2 twice).
3. Move the decimal point one place to the right, or add a zero.

   Example:

1. If the 2-digit number chosen to multiply by 2 1/2
   is 98
2. Divide by 2: 98/2 = 49
3. Divide by 2: 49/2 = 24.5.
4. Move the decimal point one place to the right: 245
5. So 98 x 2 1/2 = 245.

   See the pattern?

1. If the 3-digit number chosen to multiply by 2 1/2
   is 123
2. Divide by 2: 123/2 = 61.5
3. Divide by 2: 61.5/2 = 30.75.
4. Move the decimal point one place to the right: 307.5
5. So 123 x 2 1/2 = 307.5.

1. If the 3-digit number chosen to multiply by 2 1/2
   is 488
2. Divide by 4: 488/4 = 122
3. Divide by 2: 61.5/2 = 30.75.
4. Move the decimal point one place to the right (add a zero): 1220.
5. So 488 x 2 1/2 = 1220.

Divide by 4 when it is easy (the number is divisible by 4 if its last two digits are divisible by 4), or divide by 2 twice. This method should become an easy one.