A) 5 h 50 min
B) 6 h
C) 6 h 50 min
D) 12 h 10 min
Correct Answer: C
Solution :
Let the speed of motorboat = 36x km/h |
and speed of stream = 5x km/h |
The boat goes along with the current in 5 h 10 min i.e., \[\frac{31}{6}\text{h}\text{.}\] |
\[\therefore \] Distance \[=\frac{31}{6}\times (36+5x)\] |
\[=\frac{41x\times 31}{6}\text{km}\] |
Rate upstream \[=36x-5x=31\,\,x\,\,\text{km/h}\] |
\[\therefore \] Time taken \[=\frac{41x\times \frac{31}{6}}{31x}=\frac{41}{6}\]h = 6 h 50 min |
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