sorry, no markings allowed.........

fill the 3, pour it in the 5, fill the 3, pour it to fill the 5 leaving one litre in the 3. empty the 5. pour what's left in the 3 into the 5, fill the 3, pour it into the 5.  That's easier than the first attempt.  I don't know why I made it more complicated before.

you got it, easy when yer know how...........

yes...sounds like you really did it MD.

There's no stopping MD once he starts  

I've noticed...

What can I say... I really like my water.

Its your turn to piddle, errr Riddle, MD

Oh I thought it was for anyone to throw one out now.
I'll have to google and be back later.

I remember one.  
You sit at a table with 2 other people.  All of you are wearing either a green or a purple hat.  You can't see your own, but you can see the colour that the other 2 people are wearing.  You see that one has a green one and one has a purple one.  All of you are told that whoever guesses the colour on their own head correctly wins, and that not all 3 of you have green.  After quite a while the room is silent and you stare each other down without laughing, and you say "AHA!!!!!! mine is purple!  I am the master!  I win!  What did I win?"

How did you know what colour you had?

You sit at a table with 2 other people.  All of you are wearing either a green or a purple hat.  You can't see your own, but you can see the colour that the other 2 people are wearing.  You see that one has a green one and one has a purple one.  All of you are told that whoever guesses the colour on their own head correctly wins, and that not all 3 of you have green.  After quite a while the room is silent and you stare each other down without laughing, and you say "AHA!!!!!! mine is purple!  I am the master!  I win!  What did I win?"

How did you know what colour you had?

This is impossible from the information given  

One of the guys had glasses and you could see the reflection of your hat in them.

It was a blind guess and the guy only pretended that he knew the hat colour.

I always like this one.
If you had a green hat, then the guy with the purple hat would see you and the other guy with green hats and know his was purple because you're not all wearing green hats based on the information you were all given.  Since there's continued silence, you have to assume yours is purple or that guy would have known right away.


Easier one:
What number, when added to the number three or multiplied by it, gives the same result?