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# Thread: Brain Teaser

1. ## Brain Teaser

A while back there were a series of brain teasers posted here. One had to do with dice and being able to place numbers on each side (0-9). Anyone remember the exact question? I searched the site, but the link is outdated (originally posted by AJ). Thanks in advance for your help!

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Will Riley

2. ## Re: Brain Teaser

I think this is the text from the message - question 2 is the one I think you are refering to:

Question 1:
You have 2 unmarked containers, one with the capacity of 9 gallons, and the other 7 gallons. You have an infinite water source and you need exactly 8 gallons.
What do you do?

Question 2:
You have 2 blank cubes. You need to write on them numbers so you can create any date of any month. Basically you need to be able to display the date using them. So tell me what numbers you would write on each of them.
In short you will need to specify which numbers you put on the 2 cubes to represent the numbers between 01-31
Cube one has: X, X, X, X, X, X
Cube two has: X, X, X, X, X, X

Also here's a bonus question for you all. This one I usually ask on interviews
You have 9 dots (shown below). Connect them using 4 straight (contineous) lines without taking your hand off the paper.
code:

X X X

X X X

X X X

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Atlee

3. ## Re: Brain Teaser

No No, No answers... That's why they're called Brain Teasers!

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AJ Alhait
BetaSoft Inc.

4. ## Re: Brain Teaser

AAaahhhhhh!!! they are goind to drive me nuts!!!!!

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If you can smile when things go wrong, you have someone in
mind to blame.

5. ## Re: Brain Teaser

No offense to anyone, but compared to the Logical Questions thread, these are pretty darn easy. Check out the Logical Questions thread at

http://www.qaforums.com/Forum33/HTML/000126.html

I will not provide answers here since people seem to be in the midst of solving these. But think these through and the solutions are obvious.

For example, consider that for the cube-date question, to show all possible days, you would need one of each of the ten digits. You would also need two one's and two two's (in order to show 11 and 22). That is twelve numbers right there. So what do you have: two cubes, twelve faces. Thus every face is used. You know each cube will need a "1" and a "2". And part of one way of forming the solution is to consider an inverted number. 'Nuff said as far as hints go.

As far as the water puzzle, these are just measurement problems, although usually given in ratio format. It is usually given as something like a 3-5-4 solution, not a 9-7-8, because the solution is then ratio-based on the boundaries of the numbers. So rather than give the answer to this puzzle I will show you how to solve the 3-5-4 solution. Basically, you restate it as having a three-gallon and a five-gallon container You want ot put four gallons of water in the five-gallon container. So: fill up the three-gallon container and pour it into the five-gallon container. Do this again and you will have one gallon left in the three-gallon container. Now, empty the five-gallon container and then pour in the one gallon. Now fill the three-gallon container again and pour it into the five-gallon container. You have four gallons! Now, see if you can work that out for the 9-7-8 problem. I think you will find it interesting.

As far as the connecting-puzzle, think "outside the box." Also number the squares as that makes it easier to visualize.

[This message has been edited by JeffNyman (edited 01-21-2002).]

6. ## Re: Brain Teaser

Alright - now do we have the answers for these teasers?

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If you can smile when things go wrong, you have someone in
mind to blame.

7. ## Re: Brain Teaser

<BLOCKQUOTE><font size="1" face="Verdana, Arial, Helvetica">quote:</font><HR>Originally posted by awhiteleather:
...
Also here's a bonus question for you all. This one I usually ask on interviews
You have 9 dots (shown below). Connect them using 4 straight (contineous) lines without taking your hand off the paper.
code:

X X X

X X X

X X X

<HR></BLOCKQUOTE>
Heck, that's a golden oldie. Besides, I can connect them with one (1) straight line (and no, not a really fat line, but a genuine, 1-dimensional line).

PS: I hope you don't make hiring decisions based on such a quiz. Some people have better spatial perception skills than others, but that doesn't necessarily make them better testers, just better at solving spatial perception problems. I suppose if you were interviewing me, I'd have to make a moral decision: either tell you that I saw that puzzle when I was a kid and solved it (or read the answer, I don't remember now), or I could study it and frown a bit, then suddenly say, "Eureka!" and connect the dots with four lines.

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Charles Reace

charles{DOT}reace{AT}verizon{DOT}net

[This message has been edited by Charles Reace (edited 01-22-2002).]

8. ## Re: Brain Teaser

<BLOCKQUOTE><font size="1" face="Verdana, Arial, Helvetica">quote:</font><HR>Originally posted by Charles Reace:
Heck, that's a golden oldie .... I suppose if you were interviewing me, I'd have to make a moral decision: either tell you that I saw that puzzle when I was a kid and solved it (or read the answer, I don't remember now)....<HR></BLOCKQUOTE>

Actually this is so true! So many of these puzzles are probably on-line somewhere that it would be easy to prepare yourself for them anyway. In fact, some sites are dedicated to providing known interview "quizzes" and "common puzzles." When Microsoft was really into this it did not take long for the information to spread. Of course they then usually modify the puzzles.

But I agree - this kind of puzzle does not necessarily tell you much. You are much better off (if you are the type to go the puzzle route) to use puzzles that determine how someone thinks and not puzzles that necessarily demand a right or wrong answer. There are plenty like that. You can also get clever and take logical puzzles and frame them as questions about experiences in a given field or practice, like software development, requirements gathering, deciding between two outcomes, testing, etc.

On the other hand, there are also much easier ways to find this information out without posing puzzles. This puzzle-based or quiz-based approach does sometimes come off as a little hostile or combative.

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9. ## Re: Brain Teaser

Charles, that 4 lines puzzle I remember solving when I was 8 years old. I solved it in like 10 seconds I think. It does tell you how people think. Or basically who thinks "outside the box". There are many puzzles like that, like this one:

Draw a circular Cake.
How do Cut it 3 times only to give me exactly 8 slices?

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AJ Alhait
BetaSoft Inc.

[This message has been edited by AJ (edited 01-22-2002).]

10. ## Re: Brain Teaser

<BLOCKQUOTE><font size="1" face="Verdana, Arial, Helvetica">quote:</font><HR>Originally posted by AJ:
Draw a circular Cake.
How do Cut it 3 times only to give me exactly 8 slices?
<HR></BLOCKQUOTE>

This one sort of gives you the answer already. I thought this was usually stated as: "Into how many pieces can you slice a round cake with just three straight cuts of a knife without moving the pieces around after each cut?" The solution is then eight slices.

A better cake one, although not one I would give in a testing interview, but it is a good way to see how people think:

= = =
Say that you have a nine-inch-square cake that is two-layered, and each layer is
one and one-half inches (1 1/2) high. Each layer is covered with one-fourth-inch-thick (1/4) frosting and so are the sides. There is no frosting on the bottom at all. Now, using straight knife cuts only, how can you divide the cake into thirteen pieces so that each piece has exactly the same amount of cake and frosting? It is just as easy as the above but the thinking is slightly different.
= = =

Like the first cake one, however, these are limited to spatial tests of thinking - which is good. But it is not necessarily testing all aspects. Some of the better ones for testing how people think are the liars-truth tellers puzzles. These teach you to think logically and reason out from summarized data.

For example, consider that Liars always lie (they never tell the truth) and Truth-Tellers always tell the truth (they never lie). But you also have Normals. These people sometimes lie and sometimes tell the truth. With that here are two easy (but logically thoughtful puzzles):

Puzzle 1:
Say you have two people, Bob and Rob, each of whom is either a Liar, Truth-Teller, or Normal. They make the following statements:

Bob: Rob is a Truth-Teller.
Rob: Bob is not a Truth-Teller.

Now prove that at least one of them is telling the truth, but is not a Truth-Teller.

Puzzle 2
Same situation as above except that this time they say:

Bob: Rob is a Truth-Teller.
Rob: Bob is a Liar.

Now prove that either one of them is telling the truth but is not a Truth-Teller or prove that one of them is lying but is not a Liar.

These kinds of puzzles show how you abstract information and how you think about data that is given to you and particularly about how you think about potentially contradictory data.

[This message has been edited by JeffNyman (edited 01-22-2002).]

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