Boats and Streams— Concepts, Formulas & Shortcuts
- Downstream speed D = b + s; Upstream speed U = b − s.
- Boat speed b = (D + U)/2; Stream speed s = (D − U)/2.
- Time downstream = distance/(b + s); time upstream = distance/(b − s).
- If a boat takes k times as long upstream as downstream, then b : s = (k + 1) : (k − 1).
- Round trip over distance d takes d/(b + s) + d/(b − s) hours.
- Still-water speed is always greater than stream speed, or the boat cannot go upstream at all.
Boats and Streams Practice Questions with Answers
Attempt each question first, then open the explanation. All 18 questions below are free to read and require no signup.
Q1.A boat's speed in still water is 10 km/h and the stream flows at 2 km/h. Its downstream and upstream speeds are:
Easy- A12 and 8 km/h
- B10 and 8 km/h
- C12 and 10 km/h
- D8 and 12 km/h
Boats and Streams question 1 of 18+Show Answer & Explanation
Answer: A. 12 and 8 km/h
Explanation: Downstream = 10 + 2 = 12 km/h; upstream = 10 − 2 = 8 km/h.
Q2.A man rows 30 km downstream in 2 hours and 20 km upstream in 2 hours. His speed in still water is:
Moderate- A10 km/h
- B12 km/h
- C12.5 km/h
- D15 km/h
Boats and Streams question 2 of 18+Show Answer & Explanation
Answer: C. 12.5 km/h
Explanation: Downstream = 15 km/h, upstream = 10 km/h → still water = (15 + 10)/2 = 12.5 km/h.
Q3.If downstream speed is 15 km/h and upstream speed is 9 km/h, the speed of the stream is:
Easy- A2 km/h
- B3 km/h
- C4 km/h
- D6 km/h
Boats and Streams question 3 of 18+Show Answer & Explanation
Answer: B. 3 km/h
Explanation: Stream = (15 − 9)/2 = 3 km/h.
Q4.A boat takes twice as long to go upstream as to go downstream. The ratio of the boat's speed to the stream's speed is:
Moderate- A2 : 1
- B3 : 1
- C4 : 1
- D3 : 2
Boats and Streams question 4 of 18+Show Answer & Explanation
Answer: B. 3 : 1
Explanation: b − s = (b + s)/2 → 2b − 2s = b + s → b = 3s, so 3 : 1.
Q5.A man rows to a place 48 km away and returns in 14 hours. He can row 4 km downstream in the same time as 3 km upstream. The stream's speed is:
Difficult- A1 km/h
- B1.5 km/h
- C2 km/h
- D2.5 km/h
Boats and Streams question 5 of 18+Show Answer & Explanation
Answer: A. 1 km/h
Explanation: Let downstream = 4k, upstream = 3k. 48/4k + 48/3k = 14 → 12/k + 16/k = 14 → k = 2 → D = 8, U = 6 → stream = (8 − 6)/2 = 1 km/h.
Q6.A boat's speed in still water is 15 km/h and the stream is 5 km/h. Time taken to travel 60 km downstream is:
Easy- A3 hours
- B4 hours
- C5 hours
- D6 hours
Boats and Streams question 6 of 18+Show Answer & Explanation
Answer: A. 3 hours
Explanation: Downstream speed = 20 km/h → 60/20 = 3 hours.
Q7.A boat travels 20 km downstream in 2 hours. If the stream flows at 2 km/h, the boat's speed in still water is:
Easy- A6 km/h
- B8 km/h
- C10 km/h
- D12 km/h
Boats and Streams question 7 of 18+Show Answer & Explanation
Answer: B. 8 km/h
Explanation: Downstream speed = 20/2 = 10 km/h = b + 2 → b = 8 km/h.
Q8.A man can row 6 km/h in still water. If the stream is 2 km/h, his upstream speed is:
Easy- A2 km/h
- B4 km/h
- C6 km/h
- D8 km/h
Boats and Streams question 8 of 18+Show Answer & Explanation
Answer: B. 4 km/h
Explanation: Upstream = 6 − 2 = 4 km/h.
Q9.A boat covers 24 km upstream in 6 hours and 24 km downstream in 3 hours. The speed of the stream is:
Moderate- A1 km/h
- B2 km/h
- C3 km/h
- D4 km/h
Boats and Streams question 9 of 18+Show Answer & Explanation
Answer: B. 2 km/h
Explanation: Upstream = 4 km/h, downstream = 8 km/h → stream = (8 − 4)/2 = 2 km/h.
Q10.A boat's speed in still water is 9 km/h and the stream is 3 km/h. The time taken to cover 36 km upstream is:
Easy- A4 hours
- B5 hours
- C6 hours
- D9 hours
Boats and Streams question 10 of 18+Show Answer & Explanation
Answer: C. 6 hours
Explanation: Upstream speed = 6 km/h → 36/6 = 6 hours.
Q11.A man rows 15 km downstream and 15 km upstream, taking 1 hour more upstream. If the stream is 2 km/h, his speed in still water is approximately:
Difficult- A6 km/h
- B8 km/h
- C10 km/h
- D12 km/h
Boats and Streams question 11 of 18+Show Answer & Explanation
Answer: B. 8 km/h
Explanation: 15/(b − 2) − 15/(b + 2) = 1 → 60 = b² − 4 → b² = 64 → b = 8 km/h.
Q12.If a boat goes 30 km downstream in 3 hours and returns in 5 hours, its speed in still water is:
Moderate- A6 km/h
- B8 km/h
- C10 km/h
- D12 km/h
Boats and Streams question 12 of 18+Show Answer & Explanation
Answer: B. 8 km/h
Explanation: Downstream = 10 km/h, upstream = 6 km/h → still water = (10 + 6)/2 = 8 km/h.
Q13.A boat's still-water speed is 12 km/h and the stream is 4 km/h. Its downstream speed is:
Easy- A8 km/h
- B12 km/h
- C16 km/h
- D20 km/h
Boats and Streams question 13 of 18+Show Answer & Explanation
Answer: C. 16 km/h
Explanation: Downstream = 12 + 4 = 16 km/h.
Q14.A boat's still-water speed is 12 km/h and the stream is 4 km/h. Its upstream speed is:
Easy- A4 km/h
- B8 km/h
- C12 km/h
- D16 km/h
Boats and Streams question 14 of 18+Show Answer & Explanation
Answer: B. 8 km/h
Explanation: Upstream = 12 − 4 = 8 km/h.
Q15.If downstream speed is 18 km/h and upstream is 12 km/h, the boat's still-water speed is:
Moderate- A12 km/h
- B15 km/h
- C16 km/h
- D18 km/h
Boats and Streams question 15 of 18+Show Answer & Explanation
Answer: B. 15 km/h
Explanation: Still water = (18 + 12)/2 = 15 km/h.
Q16.If downstream speed is 18 km/h and upstream is 12 km/h, the stream's speed is:
Moderate- A2 km/h
- B3 km/h
- C4 km/h
- D6 km/h
Boats and Streams question 16 of 18+Show Answer & Explanation
Answer: B. 3 km/h
Explanation: Stream = (18 − 12)/2 = 3 km/h.
Q17.A boat takes 4 hours to travel 40 km downstream. If the stream is 2 km/h, the boat's still-water speed is:
Moderate- A6 km/h
- B8 km/h
- C10 km/h
- D12 km/h
Boats and Streams question 17 of 18+Show Answer & Explanation
Answer: B. 8 km/h
Explanation: Downstream speed = 10 km/h = b + 2 → b = 8 km/h.
Q18.A man can row at 5 km/h in still water. If the river runs at 1 km/h, the time to row 12 km upstream is:
Moderate- A2 hours
- B2.5 hours
- C3 hours
- D4 hours
Boats and Streams question 18 of 18+Show Answer & Explanation
Answer: C. 3 hours
Explanation: Upstream speed = 4 km/h → 12/4 = 3 hours.
Boats and Streams — Frequently Asked Questions
How do I find boat and stream speeds from a round trip?+
Compute downstream and upstream speeds separately from the distances and times, then take their average for the boat speed and half their difference for the stream speed.
What does "twice as long upstream as downstream" tell me?+
It fixes the ratio: U = D/2 gives b − s = (b + s)/2 ⇒ b = 3s, so the boat is three times as fast as the current.
Cleared the aptitude round? Now grab the role.
Preparation only pays off when you apply. Thousands of internships and fresher jobs across India are live on MyInternships.in right now — free to apply, no consultancy fees.