# Boat and Stream

Upstream:  जब नाव या व्यक्ति धारा के विरुद्ध चल रहे हो (When the boat moves against the current of the river)

If speed of boat or swimmer is U km/h and the speed of stream is V km/h then,

Speed of boat upstream = (U − V) km/h

Downstream: जब नाव या व्यक्ति धारा के साथ बह रहे हो या चल रहे हो (When the boat moves with the current of the river)

If speed of boat or swimmer is U km/h and the speed of stream is V km/h then,

Speed of boat downstream = (U + V) km/h

### Some Basic Formulas

Speed of boat in still water is  = ½ (Downstream Speed + Upstream Speed)

Speed of stream is     = ½ (Downstream Speed – Upstream Speed)

Example :-

1. A man can row certain distance downstream in 2 hours and returns the same distance upstream in 6 hours. If the speed of stream is 1.5 km/h, then the speed of man in still water is

Solution:

By using above formulae

= 1.5 [(6+2) / (6-2)] = 1.5 * (8/4) = 1.5 * 2 = 3km/h

1. A motor boat can move with the speed 7 km/h. If the river is flowing at 3 km/h, it takes him 14 hours for a round trip. Find the distance between two places?

Solution: By using above formulae

= [14 * (72 – 32)]/2* 7 = [14 * (49-9)]/2*7

= 14*40/2*7 = 40km