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.

**(ii) Stream**

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

Â Â Â (a) Speed of boat downstream = (x+y) km/h

Â Â Â (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

## Examples

**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