You have got two buckets of capacity 3 litres and 5 litres each and a tap. How will you exactly measure out 4 litres of water with the help of two buckets and the tap.
I'd calculate the height of 4 litres in the confines of the 5 litre bucket, then draw a line at that point and fill to there using the 3 litre bucket as a source.
so we have the OP solution: ask someone on PF
and the caveat emptor solution: kholdstare's split the difference
and the greek solution (compass and straight edge only): mine
and the high-tech engineering solution: Danger's
we still need a management solution and a CEO solution to complete the picture.
Of course VP Biden could step in at anytime with a shotgun solution but we won't consider that option for now :-)
The Apple solution is to insist the 3 liter bucket is good enough and if you aren't getting 4 liters of water from it it's because you're holding it wrong
They also insist that you fill it only with AppleTM water otherwise all warranty coverage on the bucket is void.
Using a special hose attachment that splits the stream and shapes it into two hexagons because, for whatever reason, a standard "circular" stream isn't as efficient.
That's pretty clever, Mr. Trackman, but... have you ever seen a cylindrical bucket?
My uncle owned a bucket store... I had to make buckets every day after school... we made wood buckets and steel buckets and I even made one out of a dead badger once... and I gotta tell you that not a single one of 'em was cylindrical.
fill up the 3 liter bucket, pour it into the 5 liter bucket, then fill up the 3 liter bucket again and pour it into the 5 liter until the 5 liter bucket is full. Empty the 5 liter bucket pour the remaining 1 liter from the 3 liter bucket and then fill the 3 liter bucket and fill the 5 liter bucket, the water in the 4 liter bucket is exactly 4 liters.