Thursday, February 08, 2007

Pitcher Puzzle


It seems everybody I know is applying for banking internships.

I went to an internship fair last year to scope up what jobs are available for the summer. I wasn’t that serious because I’m almost guaranteed a job with my sponsor after I graduate and therefore is not in dire need of tons of work experiences gracing my CV. My friends, however, were another matter. So I went along with them, just looking around but mainly to collect the freebies that they give away at the fair, like mugs, umbrellas, pens, squeeze toys (don’t laugh!) and the like.

The thing we noticed is that since we are second year Chemical Engineering students, we’re not actually good or knowledgeable enough for serious internships at chemical companies. They usually take third year students, so we were only left with non-chemical engineering companies. That explains why every second year in my department applies to do banking.

A friend of mine just had his interview yesterday, in which he was asked a logical puzzle question. I just thought it’s interesting to put it here.

You have in your possession a 5 litre pitcher and a 3 litre pitcher. They both have no scales on them so you can only measure exact 5 or 3 litres of water. Given a supply of water, how can you make it so that you end up with exact 4 litres of water?

Note that if you pour water out of the pitcher, it will be gone because you don’t have anything to contain the water with. In other words, you can’t solve the puzzle by: “Filling the 5 litre pitcher, pouring it into the 3 litre pitcher, so you end up with 2 litres of water in the 5 litre pitcher, putting the 2 litres aside and repeating the process so as to have another 2 litres, which makes 4.” After all, then it would not be much of a puzzle anymore.

It took me two minutes to find a solution. Do have a go at it.

Yaz.

3 comments:

Anonymous said...

so what's the answer?

yazid jay said...

I guess I'll leave that to you guys to figure out, ha ha.

Okay, okay, here are some hints:

There are two solutions that I found. If you think about it, there are only two ways to start with the problem, either fill the 5 litre pitcher to the brim, or the 3 litre one. One solution corresponds to starting with the 5 litre pitcher, the other with the 3 litre one.

Solution for the 5 litre one: fill the 5 litre pitcher, pour it into the 3 litre pitcher, and then empty the 3 litre pitcher, so now you're left with 2 litres of water inside the 5 litre pitcher. Then, pour it into the 3 litre pitcher. Fill the 5 litre pitcher again, and pour it into the 3 litre pitcher. Empty the 3 litre pitcher (though you don't have to, gee this puzzle wastes a lot of water) and you're left with 4 litres of water inside the 5 litre pitcher.

Now you know how to do it, it'll probably not be that hard to find the other solution.

Anonymous said...

Lol. Thanks.