When multiplying by a 2-digit number, we split it into two parts and multiply separately, then add the partial products.
Area Model: Break both numbers into tens and ones, then multiply each part.
Example: 23 x 45 = (20+3) x (40+5) = 800 + 100 + 120 + 15 = 1,035
Column Method:
- Multiply by the ones digit first
- Then multiply by the tens digit (add a placeholder zero)
- Add both partial products