1. The problem asks to write "fifteen hundreds" in expanded notation. 2. "Fifteen hundreds" means 15 times 100, which is $15 \times 100$. 3. Calculate the value: $$15 \times 100 = 1500$$ 4. Expanded notation breaks down a number into the sum of each digit multiplied by its place value. 5. For 1500, the digits are 1, 5, 0, and 0 from left to right. 6. The place values are 1000, 100, 10, and 1 respectively. 7. So, expanded notation is: $$1500 = 1 \times 1000 + 5 \times 100 + 0 \times 10 + 0 \times 1$$ 8. Simplify by removing terms with zero: $$1500 = 1000 + 500$$ 9. Therefore, the expanded notation of fifteen hundreds is $$1000 + 500$$.