Difficulty: Easy
Correct Answer: 24 hours
Explanation:
Given data
Concept / Approach
Step-by-step calculation
Downstream speed = 9 + 1.5 = 10.5 km/h ⇒ time = 105/10.5 = 10 hUpstream speed = 9 − 1.5 = 7.5 km/h ⇒ time = 105/7.5 = 14 hTotal time = 10 + 14 = 24 hours
Verification
Check: 10.5 × 10 = 105; 7.5 × 14 = 105.
Common pitfalls
Final Answer
24 hours
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