Aptitude - Boats and Streams
Exercise : Boats and Streams - General Questions
- Boats and Streams - Formulas
- Boats and Streams - General Questions
- Boats and Streams - Data Sufficiency 1
- Boats and Streams - Data Sufficiency 2
1.
A boat can travel with a speed of 13 km/hr in still water. If the speed of the stream is 4 km/hr, find the time taken by the boat to go 68 km downstream.
Answer: Option
Explanation:
Speed downstream = (13 + 4) km/hr = 17 km/hr.
Time taken to travel 68 km downstream = | 68 | hrs = 4 hrs. | |
17 |
2.
A man's speed with the current is 15 km/hr and the speed of the current is 2.5 km/hr. The man's speed against the current is:
Answer: Option
Explanation:
Man's rate in still water = (15 - 2.5) km/hr = 12.5 km/hr.
Man's rate against the current = (12.5 - 2.5) km/hr = 10 km/hr.
3.
A boat running upstream takes 8 hours 48 minutes to cover a certain distance, while it takes 4 hours to cover the same distance running downstream. What is the ratio between the speed of the boat and speed of the water current respectively?
Answer: Option
Explanation:
Let the man's rate upstream be x kmph and that downstream be y kmph.
Then, distance covered upstream in 8 hrs 48 min = Distance covered downstream in 4 hrs.
x x 8 | 4 | = (y x 4) | |||
5 |
44 | x =4y | |
5 |
y = | 11 | x. |
5 |
Required ratio = | y + x | : | y - x | ||||
2 | 2 |
= | 16x | x | 1 | : | 6x | x | 1 | ||||
5 | 2 | 5 | 2 |
= | 8 | : | 3 |
5 | 5 |
= 8 : 3.
4.
A motorboat, whose speed in 15 km/hr in still water goes 30 km downstream and comes back in a total of 4 hours 30 minutes. The speed of the stream (in km/hr) is:
Answer: Option
Explanation:
Let the speed of the stream be x km/hr. Then,
Speed downstream = (15 + x) km/hr,
Speed upstream = (15 - x) km/hr.
30 | + | 30 | = 4 | 1 | |
(15 + x) | (15 - x) | 2 |
900 | = | 9 | |
225 - x^{2} | 2 |
9x^{2} = 225
x^{2} = 25
x = 5 km/hr.
Video Explanation: https://youtu.be/lMFnNB3YQOo
5.
In one hour, a boat goes 11 km/hr along the stream and 5 km/hr against the stream. The speed of the boat in still water (in km/hr) is:
Answer: Option
Explanation:
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