1. The problem is to multiply 4 by 9. 2. Multiplication means adding the number 4, nine times: $$4 + 4 + 4 + 4 + 4 + 4 + 4 + 4 + 4$$. 3. Instead of adding repeatedly, we use multiplication: $$4 \times 9$$. 4. Calculate the product: $$4 \times 9 = 36$$. 5. Therefore, the answer is 36.