# Boats and Streams

Stream (s): If the water of a river is moving at a certain speed then it is called as stream.
Stillwater: If the speed of the water of a river is zero, then water is considered to be stillwater.
Speed of Boat/ Man (M): Speed of boat means speed of a boat (swimmer) in stillwater.
Downstream Speed (D.S): If the speed of boat (Swimmer) is along the direction of stream is called downstream speed or along the with stream.

Upstream Speed (U.S): If the speed of boat (swimmer) is against the direction of stream is called upstream speed or against the stream.

Points to be remember

1. If the speed of a boat in still water is 20 km/hr and the speed of stream is 8 km/hr, then find speed of the boat along the stream.
A) 26 km/hr        B) 12 km/hr
C) 28 km/hr D) 24 km/hr
Sol: Speed of the boat along the stream
= 28 kmph                          Ans: C

2. A man can row with a speed of 25 km/hr in still water. His speed against the stream is 15 km/hr. Find the rate of current.
A) 15 km/hr          B) 40 km/hr
C) 10 km/hr          D) 30 km/hr
Sol: Stream speed = 25 − 15 = 10 kmph
Ans: C
3. A boy is swimming at 26 km/hr along the stream. If the speed of the stream is 8km/hr then find the speed of the boy in the still water?
A) 15 km/hr       B) 18 km/hr
C) 34 km/hr       D) 22 km/hr
Sol: Speed of the boy in still water = 26 − 8
= 18 kmph                  Ans: B

4. When the speed of the boat in still water is 15 km/hr and the man’s downstream speed is 20 km/hr. Then find a man upstream speed.

A) 15 km/hr             B) 10 km/hr
C) 12 km/hr             D) 20 km/hr
Sol: Upstream speed = 15 − 5 = 10 kmph
Ans: B
5. A man’s downstream speed is 26 km/hr and upstream speed is 16 km/hr. Then find speed of the boat in still water.
A) 20 km/hr            B) 21 km/hr
C) 25 km/hr            D) 22 km/hr

= 21 kmph
Ans: B
6. The speed of the swimmer in upstream at 15 km/hr and downstream speed at 25km/hr. Then find the speed of current.
A) 10 km/hr            B) 15 km/hr
C) 5 km/hr              D) 8 km/hr

Ans: C

7. A man travelled 1 km distance in 15 minutes at downstream. Same distance he travelled in upstream in 30 mins. Then find the speed of the boat in still water.
A) 2 km/hr               B) 1 km/hr
C) 3 km/hr               D) 4 km/hr
Sol: Downstream speed = 4 kmph
Upstream speed = 2 kmph

8. A man travelled a distance 5 km in 12 min along stream and he travelled the same distance against the stream in 20 min then find speed of the stream.

A) 10 km/hr          B) 5 km/hr
C) 15 km/hr          D) 12 km/hr
Sol: Downstream speed = 25 kmph
Upstream speed = 15 kmph

9. The speed of the boat in still water is 24 kmph and the speed of the stream is 6 kmph find the distance travelled by the boat along the stream in 12 min.
A) 8 km        B) 10 km          C) 6 km           D) 12 km
Sol: Down stream speed = 30 kmph (24 + 6)

10. A person travelled 7 km distance in 15 minutes against the stream and the speed

11. A man travelled a distance of 27 km in 3 hours along the stream and he travelled a distance of 35 km in 5 hours against the stream then find the ratio of speed of boat in still water and the speed of the current.
A) 8 : 3         B) 8 : 1            C) 6 : 1             D) 7 : 2
Sol: Down stream speed = 9 kmph
Upstream speed = 7 kmph
Ratio of speed of boat in still water and the

12. Speed of boat in still water is 15 km/hr. The boat travels 30 km along the stream and 18 km against the stream in equal time then find the speed of the stream.
A) 3.25 km/hr         B) 3.75 km/hr
C) 4.25 km/hr         D) 4.5 km/hr
Sol: Let 'x' be the speed of the stream

13. Speed of the boat is 15 km/hr and speed of the stream is 7 km/hr find the time taken to travel 33 km along the stream.
A) 75 mins.             B) 90 mins.
C) 110 mins.           D) 45 mins.
Sol: Downstream speed = 22 kmph

14. A boat takes twice as long as to row a distance against the stream as to row the same distance with the stream. Find the ratio of speed of the boat in still water to that of speed of stream.
A) 3 : 2       B) 3 : 1         C) 1 : 3        D) 2 : 5

Sol:          down stream           upstream

15. Speed of stream is '5'/9 times speed of the boat in still water. Find the ratio of speed of boat along the stream to that of speed of
boat against the stream.
A) 7 : 3        B) 14 : 5       C) 7 : 2      D) 13 : 2
Sol:           Stream speed        Boat speed

16. Stream speed is 2/7 times of boat in still water. A boat travels 45 km against stream in 90 minutes. Then find speeds of boat in still water and stream speed.
A) 42, 12     B) 49, 14    C) 49, 12     D) 38, 14
Sol:      Boat  Stream Upstream Downstream

⇒ 5x = 30 ⇒ x = 6 kmph
Speed of boat in still water = 7 × 6 = 42 kmph
Stream speed = 2 × 6 = 12 kmph               Ans: A

17. The speed of the current is 8 km/hr and the speed of the boat in still water is 24 km/hr. A person goes along the stream to a certain point and comes back to the starting point against the stream in 3 hours of time then find the distances between the points.
A) 32 km      B) 30 km     C) 38 km     D) 24 km
Sol: Let distance between two points is 'x'
According to the questions

18. The speed of the boat in still water is 12 km/hr and speed of the stream is 4 km/hr. If the difference between the time taken when a man travels a certain distance along the stream to travel the same distance against the stream is 30 min. Then find the distance between the starting point and the destination.
A) 10 km     B) 12 km     C) 8 km     D) 6 km
Sol: Let distance between two points is 'x'
According to the question

Posted Date : 03-02-2022

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