# Brain teasers **URL:** \ **Category:** random\ **Created:** [September 19, 2004, 11:30pm UTC](https://forum.kirupa.com/t/brain-teasers/64782 "2004-09-19T23:30:48Z")\ **Posts on this page:** 20\ **Page:** 3
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 6:40pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/41 "2004-09-20T18:40:42Z")
it’s calculated as follows: wanted ones divided by possible ones. then you have to multiply the results of each time you drew. first draw: 1/4 second draw: 1/3 1/4 \* 1/3 = 1/12 1/12 is the result. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 6:43pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/42 "2004-09-20T18:43:11Z")
That includes duplicates though, right? ie 1 & 2 vs 2 & 1 jtnw ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 7:10pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/43 "2004-09-20T19:10:09Z")
actually the likelihood of them being the same (without regard for one color or the other) is 1/3, had you asked what is the likelihood of them both being red, then it would have been 1/12th. As the question is asked the first card doesn’t really count, as it just determines what the other card has to be in order to match. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 7:26pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/44 "2004-09-20T19:26:47Z")
Paradox is right. The answer is 1/3. Lots of people say 1/4 or 1/2. You can do the same with children. If a couple have two children and one of them is a boy, what is the likelihood that the other is a boy as well. That answer is 1/3 as well. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 9:15pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/45 "2004-09-20T21:15:41Z")
nother one fer u fellas A man is wearing black. Black shoes, socks, trousers, jumper, gloves, and balaclava. He is walking down a black street with all the street lamps off. A black car is coming toward him with its lights off too, but somehow manages to stop in time. How did the driver see the man? ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 9:19pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/46 "2004-09-20T21:19:07Z")
It’s daytime. 😉 jtnw ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 9:21pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/47 "2004-09-20T21:21:53Z")
He didn’t, the man was walking on the sidewalk and was never in any kind of danger… duh :sigh: 😛 ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 9:24pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/48 "2004-09-20T21:24:02Z")
nice one how did you noe jtnw arrite another one for you peeps How would you rearrange the letters in the words new door to make one word? Note: There is only one correct answer. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 9:38pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/49 "2004-09-20T21:38:40Z")
azzy, I’ve heard most of these before. I know the new door one, but I’ll let others have a chance at it. jtnw ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 9:44pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/50 "2004-09-20T21:44:25Z")
Just arrange them and make “one word”? as in “new door” —\> _arranges_ ----\> “one word” :beam: :bad: ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 9:56pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/51 "2004-09-20T21:56:49Z")
ding ding ding we have a winner ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 10:09pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/52 "2004-09-20T22:09:27Z")
> [@Hans Kilian](#): > > Paradox is right. The answer is 1/3. Lots of people say 1/4 or 1/2. > > You can do the same with children. If a couple have two children and one of them is a boy, what is the likelihood that the other is a boy as well. That answer is 1/3 as well. No it’s not, it’s 1/2 😛 It’s either a boy or a girl. ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 10:22pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/53 "2004-09-20T22:22:33Z")
arrite men heres another one. three ants were going under a door and two or them could pass by. why coudnt the third one go ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 10:53pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/54 "2004-09-20T22:53:07Z")
Someone opened the door 😜 I didn’t understand the sentence in the first place :ne: ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 20, 2004, 11:20pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/55 "2004-09-20T23:20:24Z")
no you silly the third ant was wearing high heel sandals ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 21, 2004, 3:42am UTC](https://forum.kirupa.com/t/brain-teasers/64782/56 "2004-09-21T03:42:08Z")
because it was really really fat? because it had claustrophobia? =) ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 21, 2004, 3:16pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/57 "2004-09-21T15:16:46Z")
> [@Yeldarb](#): > > No it’s not, it’s 1/2 😛 > It’s either a boy or a girl. The trick is in the wording. If you said ‘If the first child is a boy, what is the chance that both of the children are boys?’, then the answer is 1/2. But when you say ‘If one of the children is a boy, what is the chance that both the children are boys?’, then the answer is 1/3. There are four equally likely combinations that you can have 2 children. 1. first child is a boy, second child is a boy 2. first child is a boy, second child is a girl 3. first child is a girl, second child is boy 4. first child is a girl, second child is girl In three of the combinations, one of the children is a boy (1, 2 and 3). But only in one of the three (no. 1) are both children boys. So the answer is 1/3. I have a mate that still - after several years - insists that the answer is 1/2 🙂 ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 21, 2004, 3:24pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/58 "2004-09-21T15:24:25Z")
> [@Hans Kilian](#): > > But when you say ‘If one of the children is a boy, what is the chance that both the children are boys?’, then the answer is 1/3. > > There are four equally likely combinations that you can have 2 children. > > 1. first child is a boy, second child is a boy > 2. first child is a boy, second child is a girl > 3. first child is a girl, second child is boy > 4. first child is a girl, second child is girl > I have a mate that still - after several years - insists that the answer is 1/2 🙂 I insist it to be 1/2 as well! the 2nd and the 3rd are identical! IF you have 1 boy then the next one can be either a boy or a girl… it doesn’t matter if the boy is the “first” or the “second” one. ok… If the “first” one is a boy then you’re left with variants 1 and 2 (SEE? only 2!), if the boy is the “second” one then you’re left with varianbts 3 and 1 (oh look! 2 again!) … so the answer is definitely 1/2 😜 ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 21, 2004, 3:38pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/59 "2004-09-21T15:38:04Z")
> [@Hans Kilian](#): > > The trick is in the wording. If you said ‘If the first child is a boy, what is the chance that both of the children are boys?’, then the answer is 1/2. > > But when you say ‘If one of the children is a boy, what is the chance that both the children are boys?’, then the answer is 1/3. > > There are four equally likely combinations that you can have 2 children. > > 1. first child is a boy, second child is a boy > 2. first child is a boy, second child is a girl > 3. first child is a girl, second child is boy > 4. first child is a girl, second child is girl > > In three of the combinations, one of the children is a boy (1, 2 and 3). But only in one of the three (no. 1) are both children boys. So the answer is 1/3. > > I have a mate that still - after several years - insists that the answer is 1/2 🙂 Nice one 🙂 Very tricky. Here’s one of my favorite: I have 5 hats in my hands. 3 of them are white, 2 of them are black. In front of me are standing Senocular, Kirupa and Lostinbeta. I put one hat on each head, so that they can see the color of the other people’s hat but not their own. I ask them what the color of their hat is. Senocular, seeing a white hat on Kirupa’s head and a white hat on Lost’s head, and noticing that neither of them can answer the question, says “I’m wearing a white hat”. Now how did he know that ? PS: This brain teaser assumes that Senocular is a bit more clever than his 2 contestants :love: ---
**Author:** ![system](https://canada1.discourse-cdn.com/flex011/uploads/kirupa/original/3X/6/2/621e5c11736f46532526e61be85940af4230f3e5.png) [@system](https://forum.kirupa.com/u/system)\ **Post date:** [September 21, 2004, 3:45pm UTC](https://forum.kirupa.com/t/brain-teasers/64782/60 "2004-09-21T15:45:41Z")
um, you’re still holding the 2 black hats and sen notices that? =) [Previous page](https://forum.kirupa.com/t/brain-teasers/64782.md?page=2) [Next page](https://forum.kirupa.com/t/brain-teasers/64782.md?page=4)