A man travels the first 2 hours at a speed of 45 km/h, the next 3½ hours at a…
2023
A man travels the first 2 hours at a speed of 45 km/h, the next 3½ hours at a speed of 60 km/h and the next 4½ hours at a speed of 70 km/h. What is his average speed (in km/h) for the entire journey?
- A.
60.5
- B.
61.5
- C.
62
- D.
63
Attempted by 34 students.
Show answer & explanation
Correct answer: B
Key idea: Average speed = total distance ÷ total time.
Step 1: Distances for each segment: 2 × 45 = 90 km; 3.5 × 60 = 210 km; 4.5 × 70 = 315 km.
Step 2: Total distance = 90 + 210 + 315 = 615 km.
Step 3: Total time = 2 + 3.5 + 4.5 = 10 hours.
Step 4: Average speed = 615 ÷ 10 = 61.5 km/h.
Answer: 61.5 km/h