Time and Distance Formulae - 4

Rowing Downstream and Upstream

1. If a man rows 'a' boat at a kmph in still water and 'b' kmph be the velocity of the current (of the river), then man will row his boat with velocity (a + b) kmph and (a - b) kmph downstream and upstream respectively.

2. Speed of the boat in the downstream direction = Speed of boat in still water + Speed of the stream

3. Speed of the boat in the upstream direction = Speed of boat in still water - Speed of the stream.

4. Speed of the stream

		= Speed in downstream direction -	Speed in upstream direction
			2

5. Boat's speed in still water

		= Speed in downstream direction +	Speed in upstream direction
			2

Pipes and Cistern

1. Inlet : A pipe connected with a tank (or a cistern or a reservior) is called an inlet, if it fills it.

2. Outlet : A pipe connected with a tank is called an outlet, if it empties it.

Formulae

(i) If a pipe can fill a tank in x hours, then the part filled in

		1 hour =	1
			x

(ii) If a pipe can empty a tank in y hours, then the part of the full tank emptied in

		1 hour =	1
			y

(iii) If a pipe can fill a tank in x hours and another pipe can empty the full tank in y hours, then the net part filled in 1 hour, when both the pipes are opened =( ¹/_x - ¹/_y)