A boat can travel 24 km upstream and 28 km downstream in exactly 6 hours. It can also travel 30 km upstream and 21 km downstream in 6.5 hours. What is the speed of the boat in completely still water?

Correct answer: 10 km/hr

Explanation: ✅ Correct Answer: D) 10 km/hr 📚 Explanation: Let upstream speed be U and downstream be D. We get two equations: (24 ÷ U) + (28 ÷ D) = 6, and (30 ÷ U) + (21 ÷ D) = 6.5. Solving these simultaneous equations mathematically reveals that U = 6 km/hr and D = 14 km/hr. The formula for the speed of the boat in still water is (Downstream + Upstream) ÷ 2. This is (14 + 6) ÷ 2, giving exactly 10 km/hr.