UBS Interview Question: You have a 3-gallon jug, a 5-... | Glassdoor

## Interview Question

Analyst Interview

# You have a 3-gallon jug, a 5-gallon jug, and an unlimited

supply of water. How do you get exactly 4 gallons of water without estimating?
Tags:
brain teaser

41

Two possible answers, but here is one:
You fill the 5-gallon jug, then pour it into the 3-gallon jug until it is full (leaving 2 gallons in the 5-gallon jug). You pour out the 3-gallon jug completely. You then pour the 2 gallons from the 5-gallon jug into the 3-gallon jug. Lastly, you fill the 5-gallon jug and pour it into the remaining space of the 3-gallon jug (1 gallon), leaving you with 4 gallons in the 5-gallon jug.

Interview Candidate on Feb 9, 2010
56

fill up the 3 gallon tank and pour it into the 5, refill the 3 gallon again and top off the 5. This leaves 1 gallon left in the 3 gallon tank. Dump out the 5 gallon tank and pour in the 1 gallon. fill up the 3 gallon tank completely again and pour it into the 5 to make 4.

solution 2 on Feb 15, 2010
3

Fill both the 3 and 5 gallon jugs half way full...half of 3 is 1.5 and half of 5 is 2.5 together you get 4 gallons.

Anonymous on Feb 15, 2010
13

The previous answer is incorrect because the question supposes you cannot estimate "half a jug." There are no markings whatsoever on the jugs to make such measures.

Interview Candidate on Feb 15, 2010
0

When did you apply and when did you get the interview? How much was your salary? Thanks!

Hello on Feb 15, 2010
0

3X5= 15 [ place 3 full 5 gallon containers worth into a container]
3+3+5= 11 [ remove (2) 3 gallon jugs and one 5 gallon jug of water]
15-11=4 [ you are left with 4 gallons of water.]

restobitch on Feb 16, 2010
2

assuming you have a large container like the above solution, it would be better to just fill the tank with 2 full 5 gallons and then remove 2 full 3 gallons. 10 - 6 = 4.

Though I think the question is meant to assume you only have the 2 buckets.

mrlogue on Feb 16, 2010
5

Fill the 3 gallon jug and pour it into 5 gallon jug ( remaining space in 5 gallon jug = 2 gallon)
Again Fill the 3 gallon jug and pour it into 5 gallon jug ( 5 gallon jug is full, 1 gallon remaining in 3 gallon jug)
Empty 5 gallon jug and trasfer the 1 gallon remaining in the 3 gallon jug into the 5 gallon jug ( 5 gallon jug now holds 1 gallon of water)
Now fill up the 3 gallon jug and transfer it into the 5 gallon jug ( 5 gallon jug now contains exactly 4 gallons)

Anonymous on Feb 16, 2010
3

Here is another way, and you only need one of the jugs. Since you have an unlimited supply of water, fill the 5 gallon jug several times while timing the fill. Add together the total number of gallons filled with each jug filling and total the time. Divide the total time by the number of gallons. Dump the 5 gallon jug and fill for 4 x the average time to fill.

waterdoc on Feb 18, 2010

This post has been removed.

1

Wow, talk about over engineering the solution.

It's easy. Cut the 5 gallon jug in half. But the 3 gallon jug in half. Fill both halves and you've got 4 gallons. That answer show innovation, simplicity, and a quick path to results = you are hired.

Anonymous on Feb 19, 2010

This post has been removed.

4

The problem didnt say anything about where the water ended up, so i say the four gallons can end up on somebodies floor. So, Step 1. Fill up the 3 gallon jug all the way. Step 2. Now dump it into the 5 gallon jug. You should still have 2 gallons of empty space right? Now repeat steps 1 and 2. You should have displaced 1 gallon all over the floor. Now repeat step 1. You now have 1 gallon of water all over the floor and 3 gallons of water still in the bucket. But heck this problem is screwy so just dump the last 3 gallons on the floor and now you have a 4 gallon mess to clean up!

The Retarded Way, But it works! on Feb 21, 2010

This post has been removed.

3

I want to see you walk away with a job where you gave the retarded way of solving a problem during the interview. The best and easiest answers are # 1 and 2.

What? on Feb 21, 2010

This post has been removed.

3

You outsource the job and let them do it and have them send you the 4 gallons.

valleybiz on Feb 25, 2010
3

Hard to cut a glass jug in half and it may not be exact. I agree that 1 and 2 are the right answers with 1 being the standard.

Debbie on Feb 25, 2010

This post has been removed.

2

I wonder....they want you to fill up water in jugs and they dont even have the right sized jugs!...what kind of a salary will they be offering??

think! on Mar 2, 2010

This post has been removed.

1

Find the maintenance closet, return the three- and the five-gallon jugs, and retrieve the four gallon jug. Fill it. The tree-huggers love you because you have wasted no water.

Industrious on Mar 3, 2010
1

Get another much larger container, fill it 3 times with the 3 gal. jug, then remove 5 gal. with the 5 gal. jug. 3x3=9, then -5 =4.

Anonymous, Too on Mar 4, 2010
2

Sell both jugs. Use half the money to buy a 4 gallon jug. You end up with 4 gallons, a profit and less clutter in the shop. Save half the profit to invest, and use the rest to buy lunch for the staff. Hired.

Rockhill7 on Mar 5, 2010
1

Actually, if you tip a container of liquid sideways and fill it (or empty from it) so that the liquid is touching the very top of the bottom of the container and the bottom lip of the top of the container, the container is half full. Thus, filling both the 3 gallon and the 5 gallon container half way will yield 4 gallions. 1.5+2.5=4.0.

Labcritter on Mar 7, 2010
0

Fill 5-gallon-jug with water, pour over the 5-gallon-jug into 3-gallon-jug, throw away the water in 3-gallon-jug, now there's 2 gallon of water in 5-gallon-jug.

Transfer remaining water in 5-gallon-jug to 3-gallon-jug, fill the 5-gallon-jug again with water, pour the water from 5-gallon-jug to 3-gallon-jug until it's full.

Andy on Mar 8, 2010
2

Fill the 3 gallon container up and dump it in the 5 gallon container. Fill the 3 gallon up again and pour water in the the 5 gallon container until 5 gallon container is full. This leaves 1 gallon in the 3 gallon container. Dump the 5 gallon container and pour the 1 gallon of water from the 3 gallon container into the 5 gallon container. Now you have 1 gallon in the 5 gallon container. Fill up the 3 gallon and dump all 3 gallons in the 5 gallon container. Now you have 4 gallons in the 5 gallon container.

Shane on Mar 8, 2010
0

Just fill the three gallon jug half way and the 5 gallon jug half way. You will have 4 gallons of water.

Anselmo on Mar 10, 2010
0

Some of you would do poorly in an interview, especially those of you that answer a question that has already been answered. Even better is to repeat a wrong answer that has already been refuted as stupid. Please don't spit in my food when you serve me dinner tomorrow.

0

http://brainteaserbible.com/interview-brainteaser-puzzle-water-jug

JDizz on Jun 13, 2011
0

fill half of 3 gallon jug and half of 5 gallon jug and pour both into the container where you want 4 gallons of liquid.
(i.e 1.5 +2.5= 4 gallons, viola!)

Anonymous on Oct 8, 2017