A boat takes 6 minutes to cover 1 km downstream and \(7\frac{1}{2}\) minutes to cover the same distance upstream. Find the speed of the current.
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 1 km/hr
Downstream speed is boat \(+\) current and upstream speed is boat \(-\) current, so the current is half the difference of the two speeds.
Downstream: 1 km in 6 min, so speed \(\displaystyle =\frac{60}{6}=10\) km/hr
Upstream: 1 km in 7.5 min, so speed \(\displaystyle =\frac{60}{7.5}=8\) km/hr
Speed of the current \(\displaystyle =\frac{10-8}{2}=1\) km/hr