How to Multiply Two Numbers Just Over 100

Updated 4 October 2026

Multiply two numbers just above 100 in one quick step.

104 × 106 = 11024

How do you multiply two numbers just above 100?

To multiply two numbers just above 100, add the excess of one to the other number, then attach the product of the two excesses as two digits. For 104 × 106, the excesses are 4 and 6. Take 104 + 6 = 110 for the start and 4 × 6 = 24 for the last two digits, so the answer is 11024. It works because (100 + a)(100 + b) is 100 × (100 + a + b) + ab: the start counts hundreds and the product of the excesses fills the last two places. A product under 10 still takes two digits: 101 × 103 = 10403. A product of 100 or more carries into the hundreds: 112 × 115 has excesses 12 and 15, so 112 + 15 = 127 and 12 × 15 = 180, giving 12700 + 180 = 12880. Check the size first: two numbers above 100 always multiply to more than 10000.

1. 104 × 106 is a rectangle split at 100: 10000, 400, 600 and 24.

2. The three hundred-sized pieces make 100 × 110 — which is 104 + 6, or 106 + 4.

3. Only the small corner is left: 4 × 6 = 24, so 104 × 106 = 11024.

4. A corner under 10 still fills two places: 1 × 3 = 3 is written 03, so 101 × 103 = 10403.

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