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17.
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A man can row three-quarters of a kilometre
against the stream in 11 1/4 minutes. The speed (in km/hr) of the man in
still water is:
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A. 4
1/4 km/hr
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B. 5 km/hr
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C. 6 km/hr
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D. 7 km/hr
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Answer:
B.
Explanation:
Rate
upstream = [750 / 675] m/sec = 10/9 m/sec.
Rate
downstream = [750 / 450] m/sec = 5/3 m/sec.
∴ Rate in still water = 1/2 [10/9 +
5/3] m/sec = 25/18 m/sec = [25/18 * 18/5] km/hr
=
5 km/hr.
