Two Jars Solution

There are many ways to solve this problem.  Here is one way:

3 litre jar	5 litre jar	What happened
0 L	0 L	Starting point
0 L	5 L	Filled the 5 litre jar
3 L	2 L	Filled the 3 litre jar from the 5 litre jar
0 L	2 L	Dumped out the 3 litre jar
2 L	0 L	Poured the contents of the 5 litre jar into the 3 litre jar
2 L	5 L	Filled the 5 litre jar.
3 L	4 L	Topped off the 3 litre jar using contents of the 5 litre jar