Aptitude - Boats and Streams - Discussion
Discussion Forum : Boats and Streams - General Questions (Q.No. 12)
12.
A man can row three-quarters of a kilometre against the stream in 11
minutes and down the stream in 7
minutes. The speed (in km/hr) of the man in still water is:
minutes and down the stream in 7 minutes. The speed (in km/hr) of the man in still water is:Answer: Option
Explanation:
We can write three-quarters of a kilometre as 750 metres,
and 11 minutes as 675 seconds.
| Rate upstream = |  |
750 |  m/sec |
= | 10 | m/sec. |
| 675 | 9 |
| Rate downstream = | |
750 | m/sec |
= | 5 | m/sec. |
| 450 | 3 |
 Rate in still water = |
1 | |
10 | + | 5 | m/sec |
| 2 | 9 | 3 |
| = | 25 | m/sec |
| 18 |
| = | |
25 | x | 18 | km/hr |
| 18 | 5 |
= 5 km/hr.
Discussion:
42 comments Page 5 of 5.
Buny said:
10 years ago
How to find time of download stream? How it is calculated 15/2?
Sudarshan said:
10 years ago
Man Speed = 1/2 (Upstream Speed + Downstream Speed).
= 1/2 (750*4/45*60 + 750*2/15*60).
= (1/2)*(750/60)(2/15)( 2/3 + 1).
= (750*2/2*60*15) * (5/3).
= 25/18 meters/sec.
= (25/18)*(18/5) Km/hr.
= 5 Km/hr.
= 1/2 (750*4/45*60 + 750*2/15*60).
= (1/2)*(750/60)(2/15)( 2/3 + 1).
= (750*2/2*60*15) * (5/3).
= 25/18 meters/sec.
= (25/18)*(18/5) Km/hr.
= 5 Km/hr.
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