A) 1 km/h
B) 1.5 km/h
C) 1.8 km/h
D) 3.6 km/h
Correct Answer: A
Solution :
[a] Suppose he moves 4 km downstream in x h. Then, |
Speed downstream \[=\left( \frac{4}{x} \right)\,\,km/h\] |
Speed upstream \[=\left( \frac{3}{x} \right)\,\,km/h\] |
\[\therefore \] \[\frac{48}{(4/x)}+\frac{48}{(3/x)}-14\]\[\Rightarrow \]\[x=\frac{1}{2}\] |
So, speed downstream \[=8\text{ }km/h,\] |
Speed upstream \[=6\text{ }km/h\] |
Rate of the stream \[=\frac{1}{2}(8-6)km/h=1km/h\] |
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