Ok, so this question may blow your minds, or you might figure it out really easily( i think it was on Jay Leno).
You have to buckets:one bucket holds 3liters and one bucket holds 5liters, you have unlimited water, how do you get one of the buckets to hold 4 liters?
Remember: all you have is the 2 buckets and unlimited water (no mesuring tools or anything and it must be exactly 4 liters)
If you figure out the answer right away dont say it yet, wait till thursday or somthing.
GO!