Question

A man rides his bicycle 10 km at an average speed of 12 km/hr and again travels 12 km at an average speed of 10 km/hr. What is his average speed for the entire trip?

• A. 9.8 km/hr
• B. 19.8 km/hr
• C. 13.8 km/hr
• D. 10.8 km/hr

Answer 1

Answer:

D. 10.8 km/hr

Total distance travelled = 10 + 12 = 22 km Time taken to travel 10 km at an average speed of 12 km/hr = 10/12 hr Time taken to travel 12 km at an average speed of 10 km/hr = 12/10 hr Total time taken = (10/12) + (12/10) hr Average Speed = 22/(10/12 + 12/10) ⇒ (22 × 120)/(10 × 10 +12 × 12) ⇒ (22 × 120)/244 ⇒ 10.8 km/hr