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A man can row three?quarters of a kilometre against the stream in 45/4 min and return in 15/2 min. The speed of the man in still water is :1). 2 km/h2). 3 km/h3). 4 km/h4). 5 km/h |
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Answer» Solution $speed = \FRAC{distance}{time}$ => Upstream speed = $\frac{\frac{3}{4}}{\frac{45}{4} \times \frac{1}{60}}$ = $\frac{3 \times 60}{45} = 4$ km/h Downstream speed = $\frac{\frac{3}{4}}{\frac{15}{2} \times \frac{1}{60}}$ = $\frac{3 \times 2 \times 60}{15 \times 4} = 6$ km/h $\therefore$ Speed of man in still water = $\frac{1}{2}$ (downstream + upstream) = $\frac{1}{2} (6 + 4)$ = $\frac{10}{2} = 5$ km/h |
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