Boats and streams is an application of concept of speed, time and distance. Some terms frequently used in questions based on boats and streams are
(i) Still water
It implies that the speed of water is zero.
It implies that the water is moving
(iii) Downstream motion
If the motion of boat or swimmer is along the direction of stream, then such motion is known as downstream motion.
(iv) Upstream motion
If the motion of boat or swimmer is against the direction of stream, then such motion is known as upstream motion.
(i) If the speed of boat in still water is x km/h and speed of current is y km/h, then
(a) Speed of boat downstream = (x+y) km/h
(b) Speed of boat upstream = (x – y) km/h
(ii) If speed of boat down stream is u km/h and
upstream speed of boat is v km/h, then
Ex. A man rows 30 km downstream and 18 km upstream, taking 5 h each time. What is the speed of stream?
(a) 9.6 km/h
(b) 5 km/h
(c) 8 km/h
(d) 1.2 km/h