1. **State the problem:** Katie burns 150 calories in 25 minutes. We want to find how many calories she burns in 40 minutes. 2. **Set up the proportion:** Since calories burned is proportional to time worked out, we write: $$\frac{150}{25} = \frac{x}{40}$$ where $x$ is the calories burned in 40 minutes. 3. **Solve the proportion:** Cross-multiply: $$150 \times 40 = 25 \times x$$ $$6000 = 25x$$ 4. **Isolate $x$ by dividing both sides by 25:** $$\frac{6000}{\cancel{25}} = \frac{25x}{\cancel{25}}$$ $$240 = x$$ 5. **Answer:** Katie is expected to burn **240 calories** in 40 minutes. This matches the choice: 240 calories.