**Important Concepts & Tricks – Boat and Stream**

**Up Stream** – It means the boat is moving against the direction of the stream.

**Down Stream** – It means the boat is moving in the direction of the stream.

**Note- **

**Stream**means current i.e. the**speed of the water**.- When we say the speed of boat/swimmer/steamer, we mean the speed in still water.
- Speed of Boat/Steamer/swimmer is always considered greater than the speed of the current.

Let the Speed of Boat = **x km/hr**

Speed of Stream/current = **y km/hr**. Then-

Speed of Boat in Upstream = **(x – y) km/hr**

Speed of Boat in downstream = **(x + y) km/hr**

Speed of Boat = **1/2 (Speed of Boat in Upstream + Speed of Boat in downstream)**

Speed of Stream = **1/2 (Speed of Boat in downstream – Speed of a boat in Upstream)**

__Boat and Stream Examples-__

**Q- 1. A man can row upstream at 6 km/hr and downstream at 10 km/hr. Find the speed of man and the speed of the current.**

Upstream Speed= 6 km/hr

Downstream Speed = 10 km/hr

Man’s Speed = (10 + 6)/2 = 8 km/hr (Answer)

Current’s Speed = (10 – 6)/2 = 2 km/hr (Answer)

**Q- 2. A boat can travel with a speed of 11 km/hr in still water. If the speed of the stream is 6 km/hr, find the time taken by the boat to go 85 km downstream.**

**Solution- **

Downstream Speed- (11+6) = 17 km/hr

Time taken to travel 85 km- (dist./speed) = 85/17 = 5 hours (Answer)