## Boats and Streams

• Still water: The water of a river or any other water body which is not flowing is known as still water.
• Stream: It is the flowing water of a river that is moving at a certain speed.
• Upstream: The boat or a swimmer moving against the stream is known as moving upstream i.e., against the flow of water.
• Downstream: The boat or a swimmer moving along the stream is known as moving downstream i.e., along the flow of water.

### Important Formulas

• Speed of this boat downstream = (u + v) km/hr
• Speed of this boat upstream = (u -v) km/hr.
• Also, if the downstream speed is ‘a’ km/hr (suppose) and the rate upstream is b km/hr, then:
• Speed in still water will be = [1/2](a + b) km/hr
• Rate of stream is = [1/2](a – b) km/hr
• When the distance covered downstream and upstream are equal, we can write: (u + v)t1 = (u – s)t2 where t1 and t2 are a different time taken.

### Aptitude Boats and Streams Questions with Answers

1. In still water, a boat can fly at a speed of 13 km/hr. If the stream speed is 4 km / h, find the time the ship has taken to go 68 km downstream.

• A. 2 hours
• B. 3 hours
• C. 4 hours
• D. 5 hours

2. A boat that runs upstream takes 8 hours 48 minutes to cover a certain distance, whereas it takes 4 hours to cover the same downstream range. What is the ratio between boat speed and speed of water current, respectively?

• A. 2: 1
• B. 3: 2
• C. 8 : 3
• D. Cannot be determined

Answer: Option C (8 : 3)

3. A man rowing 12 km upstream takes 20 minutes, which is a third longer than the time he takes downstream on his journey. What is its speed in still water?

• A. 41 km/hr
• B. 36 km/hr
• C. 42 km/hr
• D. 45 km/hr

4. How long will it take to row 20 km upstream if the stream is allowed to row 10 km in 10 minutes in still water, and the same distance in 8 minutes?

• A. 12 min
• B. 13.33 min
• C. 24 min
• D. 26.67 min

5. A boat’s speed in still water is 15 km / h, and a current average of 3 km / h. In 12 minutes the distance traveled downstream is:

• A. 1.2 km
• B. 1.8 km
• C. 2.4 km
• D. 3.6 km

6. A boat traveling 36 miles downstream takes 90 minutes less than traveling the same distance upstream. If the boat’s speed in still water is 10 mph, the flux speed is:

• A. 2 mph
• B. 2.5 mph
• C. 3 mph
• D. 4 mph

7. In Hours a man rows ‘k’ km upstream and downstream again to the same point. In still water, the rowing speed is s km/hr, and the stream rate is r km/hr. Then there is

• A. (s2-r2) =2sk /H
• B. (r + s) = kH / (r -s)
• C. rs = kH
• D. None of the above

Answer: Option A ((s2-r2) =2sk /H)

8. A man rows upstream 24 km in 6 hours, and downstream a distance of 35 km in 7 hours. The man pace in still water is then

• A. 4.5 km/hr
• B. 4 km/hr
• C. 5 km/hr
• D. 5.5 km/hr

9. In 6 hours, a man may row 30 km upstream. If the man velocity in still water is 6 km / h, find out how much downstream he can row in 10 hours.

• A. 70 km
• B. 140 km
• C. 200 km
• D. 250 km

10. For 1 hour, a boatman travels 2 km toward the streams current and goes 1 km along with the current for 10 minutes. How long does it take in stationary water for 5 km to go?

• A. 40 minutes
• B. 1 hour
• C. 1 hr 15 min
• D. 1 hr 30 min

Answer: Option C (1 hr 15 min)

## Quote of the day!

### __________________

Knowing is not enough; we must apply.
Wishing is not enough; we must do.