At the 4 Gallon puzzle, the solution is wrong, because the measure unit is 5 and 3 so how can you measure one gallon? the solution as i see it is: fill the 3 gallon container and empty it in the 5 gallon container, then fill it up again and empty it again in the 5 gallon one; now you have in the 3 gallon container 1 gallon. empty the 5 gallon container, pour in it the 1 gallon you have in the 3 gallon container, refill the 3 gallon container and empty it in tha 5 gallon one. now you have 4 gallons.

The problem of measuring four gallons has a another solution.

Measure 3 gallons and pour into 5 gallon device. Measure 3 gallons again and pour into 5 gallon device. You are left with 1 gallon in the 3 gallon device. Empty the 5 gallon device - pour the remaining 1 gallon into the 5 gallon device, measure 3 gallons and pour into the 5 gallon device - measuring a total of 4 gallons.

Fill the 5gall and pour it into the 3gall... it has 2gall left. Empty the 3 then pour in those 2gall from the 5. Re-fill the 5 and pour off 1gall to fill the 3... 4 gallons remain.

ok Arnie if your solution is correct, then there is no need to do everything before pouring the 1 gallon out of the 5 gallon container. just fill the 5 gallon container and pour out a gallon. but see your answer can't work b/c you don't know how much 1 gallon is in the 5 gallon container, so comments #1 and #2 are correct.

The solution is,
Fill 5 gallon,
Fill 3 gallon with 5 gallon
What is left in 5 gallon?
5-3 = 2 gallons
Okay, we all got that right?

Now,
Put the 2 gallons (from 5 gallon jug) into the 3 gallon jug.
Fill 5 gallon jug again.
Follow the same procedure as before
Pouring as much water from 5 gallon into 3 gallon

But there is already 2 gallons in the 3 gallon jug, right?
3-2 = 1 gallon of space

5-1=4 gallons
That is how his procedure works.

Think it out before you criticize you guys.

C'mon people - think outside the box

Fill both the 3 gallon and 5 gallon full.
Tip both over until the level of water is at the junction of the wall and the bottom - you have just poured out half of the water (try it if you don't believe it)
Now the 3 gallon has 1.5 gallons and the 5 gallon 2.5 gallons
1.5 + 2.5 = 4

Thank you thank you - hold the applause.

fill up the 3-Gallon container using the filled 5-Gallon container. There are 2 gallons left in the 5-Gallon container. Dump the 3-Gallon Container. Pour the two gallons remaining from the 5-Gallon container into the previously empty 3-Gallon container. The 3-Gallon container now has two gallons and space for one more gallon.

The 5-Gallon container should be empty. Fill it with water; it now has five gallons. With these five gallons, pour as much as you can into the 3-Gallon container. The 3-Gallon container had room for one more gallon, so the 5-Gallon container should now have 5-1 gallons of water. 5-1=4.

i dont no da soloution

Nothing says that the measuring device is a prism. Try your technique with a conical 5 gallon and 3 gallon container.

I came to the same solution as Arnie in post 3. The other method works too but takes 8 filling and emptying stages, rather than 6.

This solution wastes alot of water..

3 5
0 5
3 2
0 2
2 0
2 5
3 4

Have any of you seen Die Hard 3?
Well, this puzzle appears in the movie: the hero (John McLane) has to solve it in order to stop a bomb.

What is the "junction of the wall and the bottom"? And, would that procedure work for everyone, or would diminishing eyesight cause inaccurate results? If you were locked in a room with a bomb, a water faucet, a five gallon container, and a three gallon container -- and the only way to disarm the bomb was to pour exactly four gallons of water into a measuring container that was wired into the bomb... well who cares. That situation will most likely never come up, and in this world we live in thinking outside the box is a great talent. Kudos, Bob. Kudos.

I love you Bob

I don't know why everyone's arguing about it.
The first post has the right answer in it.
You don't need to overcomplicate things.
:]

bob bob bob rulzz roflmao

OK!
Why can't you:
- Fill the 5 gallon container.
- Pour from the 5 gallon container into the 3 gallon container filling the 3 gallon container and leaving 2 gallons in the 5 gallon container.
- Empty the 5 gallon container into a seperate container which holds an unknown amount that is over 2 gallons.
- Refill the 5 gallon container.
- Pour the 5 gallon container into the empty 3 gallon container leaving 2 more gallons in the 5 gallon container.
- With the two seperate 2 gallons added together, it gives you 4 gallons.

EASY!

You can't do that because the crazy bomber guy only gives john mclane and zeus a 3gal and a 5 gal. there is no third container. C'mon guys I though this was a really popular movie.

a possible solution cud b
1) fill the 5 gallon container and pour it into the 3-gallon container as along as it is full
2) now,in the 5-gallon jar there is 2-gallon liquid....empty the 3-gallon-container and pour the liquid left in the 5-gallon-container which is nw 2-gallons into the 3-gallon-container....
3)refill the 5-gallon-container...
4)pour into the 3-gallon-container till full...
5)now in the 5-gallon-container v r left with 4 gallon liquid...

I've known that one forever. Try measuring all of the gallons from 4 gallons to 13 gallons with a 4-gallon jar and a 9-gallon jar (not simultaneously)! It is possible.

Half fill both...

3 gallon contains 1.5
5 gallon contains 2.5

pour the 1.5 into the 2.5 = 4 Gallons!

just fill up the 3 gallon then empty into the 5 gallon then fill up the 3 again nd fill the 5 gallon leaving one gallon now empty the 5 gallon on the floor put the one gallon in and then another 3 gallon = 4 gallons in the 5 gallon jug :(

you keep talking about outside the box. but you need the water IN the box.

put the 3 liter container INSIDE the 5 liter contaner.
add water to the top of the 5 liter container. (it will only get 2 liters worth since 3 liters of it is filled up by the other jug)
add the 2 liters into the 3 liter jug.
add water to the 5 liter jug again, and then add the 2 liters from the 3 jug to the 2 liters of the 5 jug

Step 1: Put 3L jug inside 5L jug = 2L empty space
put 2L water from 5L jug into 3L jug
repeat Step one.
put 2L from the 3L jug into the 5L which now contains 2 liters.

The only problem i could see is if the jug takes up more then 3l due to thickness. then we might have slightly less then 2L

Fill Each up half way. 1.5 + 2.5 = 4

So did anybody else think it is retarded to say you need to pour out all but 2 gallons when you don't have any way of measuring 2 gallons except to say that it is closer to filling the 3 gallon container than to making it totally empty?

i like your all work. keep work on it.

The solution is harder than what you can do. First you fill the 3 gallon container.
Next empty that into the 5 gallon container.
Now you have 3 gallons in the 5 gallon container.
Fill the 3 gallon container.
Pour all of that into the 5 gallon container.
Now you have the 3 gallon container with 1 gallon of the liquid.
Empty the 5 gallon container.
Then fill the 5 gallon container with the 1 gallon from the 3 gallon container.
The 5 gallon container has 1 gallon.
Fill the 3 gallon container.
Finally you will pour the 3 gallons into the 5 gallon container.

That was way to easy for me! I have ssen Die hard 3 and I had thought of that when I was checking my answers~!