1.
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What is the speed of the boat in still water?
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I.
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The speed downstream is 12 kmph.
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II.
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The speed upstream is 4 kmph.
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III.
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In a to and fro journey between two points, the average speed of the boat was 6 kmph.
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I and II only
All I, II and III
III, and either I or II
Any two of the three
None of these
Answer: Option
Explanation:
| From I and II, the speed of the boat in still water = |
1 |
(12 + 4) km/hr = 8 km/hr. |
| 2 |
From II and III, we get:
| Using average speed = |
2xy |
, we get: |
2 x 4 x y |
= 6 |
| x + y |
4 + y |
8y = 24 + 6y
y = 12.
 Required speed = |
1 |
(12 + 4) km/hr = 8 km/hr. |
| 2 |
Similarly, I and III also give the answer.
The correct answer is (D).
why x is taken as downstream in 3rd case?
