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 average speed were 50 km/h, the car would have taken longer to cover 150 km. Specifically, it would take \( \frac{150 \text{ km}}{50 \text{ km/h}} = 3 \text{ hours} \), which is not the case here. - **Option C: 100 km/h**: This option is also incorrect. If the car traveled at an average speed of 100 km/h, it would cover 150 km in \( \frac{150 \text{ km}}{100 \text{ km/h}} = 1.5 \text{ hours} \). This is less than the 2 hours mentioned in the problem. - **Option D: 120 km/h**: This option is incorrect as well. If the car traveled at 120 km/h, it would take \( \frac{150 \text{ km}}{120 \text{ km/h}} = 1.25 \text{ hours} \) to cover the distance, which again is less than the 2 hours stated. ### 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 rounding numbers during calculations; always keep the full number until the final answer. ### 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 is \(75 \text{ km/h}\). - Always check that your units are consistent (distance in km, time in hours). - Be aware of common pitfalls, such as confusing average speed with instantaneous speed.