| Speed of motorboat in still water is 45 km/h. If the motorboat travels 80 km along the stream in 1 h 20 min, then the time taken by it to cover the same distance against the stream will be [SSC (CPO) 2008] |
A) 3 h
B) 1 h 20 min
C) 2 h 40 min
D) 2 h 55 min
Correct Answer: C
Solution :
| Let the speed of the current \[=x\,\,km/h\] |
| \[\therefore \]Rate downstream \[=(x+45)km/h\] |
| According to the question, |
| \[\frac{80}{x+45}=1\,\,h\,\,20\min =\frac{4}{3}h\] |
| \[\Rightarrow \] \[4x+180=240\] |
| \[\Rightarrow \] \[4x=240-180=60\] |
| \[\Rightarrow \] \[x=\frac{60}{4}=15km/h\] |
| Rate upstream \[=45-15=30\,\,km/h\] |
| \[\therefore \]Required time \[=\frac{80}{30}h=2\,\,h\,\,40\min \] |
You need to login to perform this action.
You will be redirected in
3 sec
