How to Multiply by 9, 99, 999, 9999 Faster

Before I explain the previous post about multiplication, I would like to discuss first multiplication by 9, 99, 999, 9999 or any number whose digits are all 9. For example, how do we multiply 87 × 99? To multiply by numbers whose digits are all 9, we just add 1 to 9, 99, 999, 9999 and so on and […]

Multiplying 2 Digit Numbers Fast

The usual steps that we in multiplying 2 digit numbers is to multiply vertically as shown in the first figure. We first use the digits ones digit of the multiplicand (12) and distribute to the ones and tens digit of the multiplier (34) shown in Step 1 and Step 2 and write the products. Then, we multiply the tens digit […]