| A man rows 12 km in 5 h against the stream, the speed of current being 4 km/h. What time will be taken by him to row 15 km with the stream? [SSC (10+2) 2015] |
A) \[1\,h\,\,26\frac{7}{13}\min \]
B) \[1\,h\,\,25\frac{7}{13}\min \]
C) \[1\,h\,\,24\frac{7}{13}\min \]
D) \[1\,h\,\,27\frac{7}{13}\min \]
Correct Answer: A
Solution :
| Let the speed of boat be x km/h, |
| Speed of upstream be \[(x-4)km/h.\] |
| According to the question, |
| \[\frac{12}{x-4}=5\] |
| \[\Rightarrow \] \[12=5x-20\]\[\Rightarrow \]\[x=\frac{32}{5}km/h\] |
| \[\therefore \] Time taken to row 15 km with the stream |
| \[=\,\,\frac{15}{\frac{32}{5}+4}=\frac{15\times 5}{52}=\frac{75}{52}\] |
| \[=1\frac{23}{52}\times 60=1\,h\,\,26\frac{7}{13}\min \] |
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