The speed of a boat in still water and the speed of the stream are in the ratio 5 : 1. The downstream speed of the boat is 30 km/hr. What is its upstream speed?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 20 km/hr
Write the two speeds as \(5k\) and \(k\). Downstream they are added, upstream the stream is taken away.
Boat \(=5k\), stream \(=k\)
Downstream: \(5k+k=6k=30\), so \(k=5\)
Boat \(=25\) km/hr, stream \(=5\) km/hr
Upstream speed \(=25-5=20\) km/hr