Multiply by 99 Trick

Problem

Multiplying by 99 requires long multiplication with carrying.

Solution

Multiply by 100 and subtract the original number.

Benefit

Converts difficult multiplication into simple subtraction.

Example

46 × 99:
46 × 100 = 4600
4600 - 46 = 4554

73 × 99:
73 × 100 = 7300
7300 - 73 = 7227