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Important Tips: Boats and Streams | Quantitative Aptitude for SSC CGL PDF Download

Downstream

When the boat's direction aligns with the flow of water, it is referred to as downstream.

Upstream

When the boat's direction opposes the flow of water, it is termed as upstream.

Important Tips: Boats and Streams | Quantitative Aptitude for SSC CGL

Type 1: Tips and Tricks for Boats and Streams questions on Finding Speed of Boat

Boats and Streams Tips and Trick and Shortcuts

Speed of the boat in still water = 1/2 (Downstream speed + Upstream speed)
Downstream speed = Speed of boat in still water + Speed of stream
Upstream speed = Speed of boat in still water – Speed of stream

Q1: A man rows a boat at 12 km/h along the stream and 8 km/h against the stream. Find the speed of the boat in still water.
(a) 12km/hr
(b) 10km/hr
(c) 15km/hr
(d) 8km/hr
Ans: 
(b)
Downstream speed of the boat = 12 km/h
Upstream speed of the boat = 8 km/h
Speed of the boat in still water = 1/2*(Downstream speed + Upstream speed)
= 1/2 (12 + 8)
= 10 km/h

Type 2: Tips and Tricks to Find the Speed of Stream

Tips and Trick and Shortcuts for Boats and Streams

Speed of stream = 1/2 *(Downstream speed – upstream speed)
Speed downstream = (u + v ) km/hr.
Speed upstream = (u – v ) km/hr.

Q1: A boat whose speed in 15 km/hr in still water goes 30 km downstream and it takes 4 hours 30 minutes to come back. Find the speed of the stream?
(a) 25km/hr
(b) 15m/hr
(c) 20km/hr
(d) 5km/hr
Ans:
(d)
Let the speed of the stream = x
Therefore, speed downstream = 15 + x
Speed upstream = 15 – x
30/(15+x) + 30/(15-x) = 4hr 30 min
30/(15+x)+ 30/(15-x) = 9/2
On solving we get
x = 5km/hr

Type 3: Using Man’s Still Water Speed Calculate Stream’s Speed

Q1: A sailor can row 6 km/h in still water. It takes him twice as long to row up as to row down the river. Find the speed of the stream.
(a) 6 km/ hr
(b) 5 km/ hr
(c) 3 km/ hr
(d) 2 km/ hr
Ans:
(d)
Let sailor’s speed in upstream = x
Downstream speed = 2x (As given in the question, his downstream speed is twice of upstream speed)
Man’s speed in still water = 1/2 (Upstream speed + Downstream speed)
= 1/2 (x + 2x) = 3x/2
3x/2 = 6 (sailor can row 6 km/h in still water)
x = 4 km/hr
Therefore, upstream speed = x = 4 km/hr
Downstream speed = 2x = 2 * 4 = 8 km/hr
Speed of stream = 1/2*  (Downstream speed – Upstream speed)
= 1/2 (8 – 4)
= 2 km/ hr

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FAQs on Important Tips: Boats and Streams - Quantitative Aptitude for SSC CGL

1. What is the difference between downstream and upstream in the context of boats and streams?
Ans. In the context of boats and streams, downstream refers to the direction in which the water is flowing, while upstream refers to the opposite direction, against the flow of water.
2. How does the current affect a boat's speed when going downstream?
Ans. When a boat is moving downstream, the current assists its movement, resulting in an increase in speed compared to when the boat is stationary or moving against the current.
3. What strategies can be used to navigate a boat efficiently when going upstream?
Ans. To navigate a boat efficiently when going upstream, it is recommended to steer closer to the riverbank where the current is slower, use a higher power setting, and adjust the angle of the boat to minimize resistance from the current.
4. Is it easier to control a boat when going downstream or upstream?
Ans. Generally, it is easier to control a boat when going downstream as the current assists its movement. When going upstream, the boat needs more power and maneuvering to overcome the resistance from the current.
5. What factors should be considered when determining the direction to travel in a stream or river?
Ans. When determining the direction to travel in a stream or river, factors such as the strength and speed of the current, obstacles in the water, wind direction, and the intended destination should be considered. It is often more efficient to travel downstream if possible, but the specific circumstances should be taken into account.
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