1) A man swims downstream 40 km in 4 hours and upstream 24 km in 3 hours. Find his speed in still water. A) 9 km/hr B) 10 km/hr C) 11 km/hr D) 12 km/hr E) 13 km/hr Answer: Option AExplanation:Downstream speed $=\frac{40}{4}$ $=10$ km/hr Upstream speed $=\frac{24}{3}$ $=8$ km/hr Speed in still water $=\frac{1}{2}(10 + 8)$ = 9 km/hr.
