Congrats to Crammarc for posting a correct solution to Puzzle #2. Here is an alternate solution:
Fill the five gallon bucket. Poor three gallons from the five gallon bucket in the three gallon bucket. Spill out the three gallon bucket. Put the remaining two gallons into the three gallon bucket. So right now we have two gallons in the three gallon bucket, and an empty five gallon. Fill the five gallon bucket again. Top off the three gallon bucket. You now have four gallons in the five gallon bucket.
Here's the third puzzle. It's a video this time, because reading walls of text gets boring.
I'm unsure of the author of the video, but it's from break.com.
Explain the differences in area, when the same pieces are used.
On a side note. Do you guys think these puzzles are too easy? I can up the ante if you want. Leave a comment, especially if you think you know the answer.