A) 11 km/h
B) 22 km/h
C) 12 km/h
D) 20 km/h
Correct Answer: B
Solution :
Let the speed of the motorboat in still water be x km/h. Then, speed downstream = (x + 2) km / h, Speed upstream = (x - 2) km / h \[\frac{6}{x+2}+\frac{6}{x-2}=\frac{33}{60}\] \[\Rightarrow \] \[11{{x}^{2}}-240\,x-44=0\] \[\Rightarrow \] \[11{{x}^{2}}-242\,x+2x-44=0\] \[\Rightarrow \] \[(x-22)\,(11x+2)=0\] \[\Rightarrow \] \[x=22\] Hence, speed of motorboat in still water = 22 km/h.You need to login to perform this action.
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