Lets understand the meaning of boat travelling upstream and downstream.
Boat travelling against the flow of stream is called Upstream
If speed of boat in still water is 10 km/hr and speed of stream is 2 km/hr
Then speed of boat in upstream will be (10 – 2) = 8 km/hr
Speed of boat in upstream =
Speed of boat in still water – Speed of stream
Boat travelling with the flow of stream is called Downstream
If speed of boat in still water is 10 km/hr and speed of stream is 2 km/hr
Then speed of boat in downstream will be (10 + 2) = 12 km/hr
Speed of boat in downstream =
Speed of boat in still water + Speed of stream
If speed of boat in still water is x km/hr
If speed of stream is y km/hr
Then speed of boat in upstream will be (x – y) km/hr
If speed of boat in still water is x km/hr
If speed of stream is y km/hr
Then speed of boat in downstream will be (x + y) km/hr