What is the speed of the boat in still water? I. Upstream speed is 4 km/h. II. Downstream speed is 6 km/h.
Verbal Reasoning
Data Sufficiency
Difficulty: Easy
Choose an option
Answer
Correct Answer: Both statements together are necessary
Explanation
Introduction / Context:Let u be boat speed in still water; v be stream speed. Upstream = u − v; downstream = u + v.
Reasoning:
- I: u − v = 4 (two unknowns, one equation) ⇒ insufficient.
- II: u + v = 6 ⇒ insufficient alone.
- I + II: Solve u = ( (u − v) + (u + v) ) / 2 = (4 + 6)/2 = 5 km/h. Sufficient.
Final Answer:Both statements together are necessary.