1. **State the problem:** Calculate the density of a block of aluminum with volume 15.0 ml and mass 40.5 g. 2. **Formula:** Density $\rho$ is defined as mass divided by volume: $$\rho = \frac{m}{V}$$ where $m$ is mass and $V$ is volume. 3. **Apply the formula:** $$\rho = \frac{40.5}{15.0}$$ 4. **Simplify the fraction:** $$\rho = \frac{\cancel{40.5}}{\cancel{15.0}} = 2.7$$ 5. **Interpretation:** The density of the aluminum block is $2.7$ g/ml. This means each milliliter of aluminum weighs 2.7 grams. Final answer: **Density = 2.7 g/ml**