| A boat moves downstream at the rate of 1 km in \[7\frac{1}{2}\min \]and upstream at the rate of 5 km an hour. What is the speed of the boat in the still water? |
A) \[3\frac{1}{2}\,\,km/h\]
B) 8 km/h
C) \[6\frac{1}{2}\,\,km/h\]
D) 4 km/h
Correct Answer: C
Solution :
| Speed of downstream \[=\frac{60}{7.5}\times 1=8\,km/h\] |
| Speed of upstream = 5 km / h |
| \[\therefore \] Speed of boat in still water |
| \[=\,\,\frac{8+5}{2}=\frac{13}{2}=6\frac{1}{2}\,\,km/h\] |
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