To determine the average speed of the car during its journey, we need to use the formula for average speed, which is defined as the total distance traveled divided by the total time taken. ### Step-by-Step Explanation: 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. **Use the Average Speed Formula**: - The formula for average speed (v) is: \[ v = \frac{\text{Total Distance}}{\text{Total Time}} \] - Plugging in the values we have: \[ v = \frac{150 \text{ km}}{2 \text{ hours}} \] 4. **Perform the Calculation**: - Now, we divide 150 by 2: \[ v = 75 \text{ km/h} \] 5. **Conclusion**: - The average speed of the car during this journey is **75 km/h**. ### Correct Option: - The correct answer is **B. 75 km/h**. ### Explanation of Other Options: - **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: \[ \text{Time} = \frac{150 \text{ km}}{50 \text{ km/h}} = 3 \text{ hours} \] This is not consistent with the given time of 2 hours. - **C. 100 km/h**: This option is also incorrect. If the average speed were 100 km/h, the time taken would be: \[ \text{Time} = \frac{150 \text{ km}}{100 \text{ km/h}} = 1.5 \text{ hours} \] Again, this does not match the 2 hours stated in the problem. - **D. 150 km/h**: This option is incorrect as well. If the car traveled at 150 km/h, the time taken would be: \[ \text{Time} = \frac{150 \text{ km}}{150 \text{ km/h}} = 1 \text{ hour} \] This is significantly less than the 2 hours mentioned. ### Common Pitfalls: - **Misunderstanding Average Speed**: Some students may confuse average speed with instantaneous speed. Average speed is calculated over the entire journey, not just at a single point. - **Incorrect Unit Conversion**: Ensure that distance and time are in compatible units (kilometers and hours in this case). - **Rounding Errors**: Be careful with calculations; ensure that you perform division accurately. ### Revision Summary: - Average speed is calculated as total distance divided by total time. - For this problem, the average speed is 75 km/h. - Always check that your calculated time aligns with the given time in the problem. - Be cautious of unit consistency and calculation accuracy.