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A swimmer swims from a point A against a current for 5 minutes and then swims backwards in favour of the current for next 5 minutes and comes to the point B. If AB is 100 metres, the speed of the current (in km per hour) is :
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- 0.4
- 0.2
- 1
- 0.6
- 0.4
Correct Option: D
Let A , B and C are the any three points lie on a line .
The distance covered upstream = AC = d
Given , AB = 100
BC = 100 + d
Rate upstream = (p – q) m/minute
Rate downstream = (p + q) m/minute
| ∴ | = 5 | |
| p - q |
⇒ d = 5 (p – q) ....(i)
| Again, | = 5 | |
| p + q |
| ⇒ | = 5 { By (i) } | |
| p + q |
⇒ 100 + 5p – 5q = 5p + 5q
⇒ 10y = 100
⇒ q = 10 m/minute
| q = | × 60kmph = 0.6 kmph | |
| 1000 |
