1. **State the problem:** We have a gas with an initial volume of 1500 cm³. It is heated until its volume increases by 20%. We need to find the new volume. 2. **Formula and explanation:** To find the new volume after an increase of 20%, we use the formula: $$\text{New Volume} = \text{Original Volume} + (\text{Percentage Increase} \times \text{Original Volume})$$ or equivalently, $$\text{New Volume} = \text{Original Volume} \times (1 + \frac{\text{Percentage Increase}}{100})$$ 3. **Calculate the new volume:** Given: $$\text{Original Volume} = 1500 \text{ cm}^3$$ $$\text{Percentage Increase} = 20\%$$ Using the formula: $$\text{New Volume} = 1500 \times (1 + \frac{20}{100})$$ 4. **Simplify the expression:** $$\text{New Volume} = 1500 \times (1 + 0.20)$$ $$\text{New Volume} = 1500 \times 1.20$$ 5. **Calculate the final value:** $$\text{New Volume} = 1800 \text{ cm}^3$$ **Answer:** The new volume of the gas is **1800 cm³**.