To determine the average speed of the car, we can use the formula for average speed, which is defined as the total distance traveled divided by the total time taken. The formula is: \[ \text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}} \] ### Step-by-Step Calculation 1. **Identify the Total Distance**: The car travels a total distance of 150 kilometers. 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 car were traveling at 50 km/h, it would take longer to cover 150 kilometers. Specifically, it would take 3 hours (150 km ÷ 50 km/h = 3 hours), which does not match the given time of 2 hours. - **Option C: 100 km/h**: This option is also incorrect. If the car were traveling at 100 km/h, it would cover 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: 120 km/h**: This option is incorrect as well. At 120 km/h, the car would cover 150 kilometers in 1.25 hours (150 km ÷ 120 km/h = 1.25 hours), which again does not match the 2 hours given. ### 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. - **Incorrect Unit Conversion**: Ensure that the distance is in kilometers and time is in hours when calculating speed in km/h. - **Rounding Errors**: Be careful with calculations to avoid rounding errors that could lead to incorrect answers. ### Revision Summary - Average speed is calculated using the formula: Average Speed = Total Distance / Total Time. - For this problem, the car travels 150 km in 2 hours, resulting in an average speed of 75 km/h. - The correct answer is option B (75 km/h). - Always check that your units are consistent and be aware of the difference between average and instantaneous speed.