A) 2
B) 2.5
C) 3
D) 2.7
E) None of these
Correct Answer: A
Solution :
Let the distance travelled upstream by the boat be D km. Then, the distance travelled downstream by the boat = (D + 12) km Now, speed of the current \[=\frac{1}{2}\](Downstream speed ? Upstream speed) \[=\frac{1}{2}\left( \frac{D+12}{3}-\frac{D}{3} \right)=\frac{1\times 12}{2\times 3}=2\,\,kmph\] Quicker Approach: Downstream coverage is 12 km more than upstream coverage in 3 hrs. \[\Rightarrow \]Downstream speed is \[\frac{12}{3}=4\]km/hr more than upstream. Thus, we know that speed of current\[=\frac{1}{2}\times 4=\frac{4}{2}=2\]km/hr.
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