To determine the average speed of the car, we need to use the formula for average speed, which is defined as the total distance traveled divided by the total time taken. The formula can be expressed as: \[ \text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}} \] ### Step-by-Step Calculation 1. **Identify the Total Distance**: The car travels a total distance of 150 kilometers to the east. 2. **Identify the Total Time**: The time taken for this journey is 2 hours. 3. **Substitute the Values into the Formula**: Now, we can substitute the values into the average speed formula: \[ \text{Average Speed} = \frac{150 \text{ km}}{2 \text{ hours}} \] 4. **Perform the Division**: Now, we perform the division: \[ \text{Average Speed} = 75 \text{ km/h} \] ### Conclusion The average speed of the car is **75 km/h**. Therefore, the correct option is **B**. ### Explanation of Other Options - **Option A: 50 km/h**: This option is incorrect because if the average speed were 50 km/h, the car would have taken longer to cover 150 kilometers. Specifically, it would take 3 hours (150 km ÷ 50 km/h = 3 hours), which contradicts the given time of 2 hours. - **Option C: 100 km/h**: This option is also incorrect. If the average speed were 100 km/h, the car would have covered 150 kilometers in 1.5 hours (150 km ÷ 100 km/h = 1.5 hours), which is less than the 2 hours stated in the problem. - **Option D: 150 km/h**: This option is incorrect as well. If the car traveled at 150 km/h, it would have covered 150 kilometers in just 1 hour (150 km ÷ 150 km/h = 1 hour), again contradicting the 2-hour travel time. ### Common Pitfalls - **Misunderstanding Average Speed**: Some students may confuse average speed with instantaneous speed. Average speed is calculated over the entire journey, while instantaneous speed refers to the speed at a specific moment. - **Ignoring Units**: Always ensure that the units are consistent. In this case, both distance and time are in kilometers and hours, respectively, which is appropriate for calculating speed in km/h. - **Calculation Errors**: Double-check division calculations to avoid simple arithmetic mistakes. ### Revision Summary - Average speed is calculated using the formula: \(\text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}}\). - For this problem, the average speed of the car is 75 km/h. - Always ensure units are consistent when calculating speed. - Be cautious of common pitfalls such as confusing average speed with instantaneous speed or making arithmetic errors.