| Sameer can row a certain distance downstream in 24 h and can come back covering the same distance in 36 h. If the stream flows at the rate of 12 km/h. Find the speed of Sameer in still water. |
A) 30 km/h
B) 15 km/h
C) 40 km/h
D) 60 km/h
E) None of these
Correct Answer: D
Solution :
| Let the speed of Sameer in still water be x km/h, |
| Sameer's speed downstream \[=(x+2)km/h\] |
| Sameer's speed upstream \[=(x-12)km/h\] |
| According to the question, |
| \[24\,\,(x+12)=36\,\,(x-12)\] |
| \[\Rightarrow \] \[2x+24=3x-36\] |
| \[\Rightarrow \] \[x=36+24=60km/h\] |
| Alternate Method |
| Here, \[x=24\,\,h,\]\[y=36h,\] |
| Rate of stream \[=12\,\,km/h\] |
| According to the formula, |
| Speed of Sameer in still water\[=\frac{a\,\,(x+y)}{(y-x)}\] |
| \[=\frac{12\times (24+36)}{(36-24)}=\frac{60\times 12}{12}=60\,\,km/h\] |
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