A car travels at a speed of 62 km/hr for 2.5 hours and then at a speed of 48 km/hr for 1.5 hours. Its average speed is approximately ______.

Correct option is D

The correct answer is (D) 56.8 km/hr

Explanation:
• Average speed is defined mathematically as the Total Distance Traveled divided by the Total Time Taken.
• Step 1: Calculate the distance of each segment.
Distance 1 = Speed 1 × Time 1 = 62 km/hr × 2.5 hr = 155 km.
Distance 2 = Speed 2 × Time 2 = 48 km/hr × 1.5 hr = 72 km.
• Step 2: Calculate the total distance and total time.
Total Distance = 155 km + 72 km = 227 km.
Total Time = 2.5 hr + 1.5 hr = 4.0 hours.
• Step 3: Calculate the average speed.
Average Speed = 227 km / 4.0 hr = 56.75 km/hr.
• This value is approximately 56.8 km/hr.

Information Booster:
• Average Speed vs. Average Velocity: Average speed is a scalar quantity (focusing on distance), while average velocity is a vector quantity (focusing on displacement over time). If a car completes a round trip and returns to its start, its average velocity is zero, but its average speed is not.
• Harmonic Mean Shortcut: If a vehicle covers two *equal distances* at different speeds (v1 and v2), the average speed formula simplifies to 2v1v2 / (v1 + v2). This does not apply here because distances are different.

Additional Knowledge:
• Option A, B, C: These are mathematical miscalculations. A common error (leading to 55 km/hr) is simply averaging the two speeds: (62 + 48) / 2 = 55. However, this is fundamentally incorrect because the car spent different amounts of time driving at each speed, requiring a weighted calculation based on total distance.