Ancient Domains Of Mystery, forum overview / General / Mathematical "mystery"
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Morio Registered user Holy Champion of ADoM Last page view: 3905 days, 12 hours, 7 minutes and 32 seconds ago. |
-1 = 1 -1 = i * i = sqrt(-1) * sqrt(-1) = sqrt((-1)*(-1)) = sqrt(1) = 1 sqrt = sqareroot i = sqrt(-1) Solution: Spoiler
sqrt(-1) * sqrt(-1) isn't actually sqrt((-1)*(-1)). Eventhough sqrt(4) * sqrt(4) is sqrt(4*4). This has something to do with the fact that you have a negative number under the squareroot "I don't know what World War 3 will be fought with, but I know World War 4 with be fought with sticks and stones." - Albert Einstein |
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Maastonakki Registered user A cute puppy Last page view: 5830 days, 17 hours and 54 minutes ago. |
Here's also anothre mystery I read from some page with odd stuff: Okay, 3 doors, in one of those doors there's a car, in two of those a goat. Choose one door. Before opening the door, a guy opens one of the remaining two doors, the opened door has a goat in it. So, we have 2 doors left. Are the odds better for winning the car if the dude chances his choise? Logic says nay, but in theory they are, see: 3 doors, pick one = 1/3 chance When the guy opens one of those 3 doors, the odds are: 2 doors, pick one: 1/2 chance... It's a conflict between logic & mathematic! |
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Ekaterin Moderator on this forum Last page view: 5772 days, 19 hours, 26 minutes and 52 seconds ago. |
This is commonly known as the Monty Hall Problem, and it's important to note that Monty Hall (the guy who opens the door with the goat) knows where the car is, and will always show you a goat. In that case, the chances of winning the car are 2/3 if you change your choice and 1/3 if you stick with your first choice. There are many ways of explaining this counterintuitive result. Perhaps the simplest is that if you stick with your first choice, you will win if and only if (iff) you had the car door in the first place (a 1/3 chance). If you switch, you will win iff you didn't have the car door to begin with (a 2/3 chance). |
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Maastonakki Registered user A cute puppy Last page view: 5830 days, 17 hours and 54 minutes ago. |
Btw, offtopic maybe, but what's the answer to this: There are 2 doors, 2 guys, one guarding each door. other door leads to hell, other to heaven. The other guy ALWAYS lies and the other guy ALWAYS tells the truth. You have one question to ask, what should you ask if you wanted to be sure to get to heaven? A teacher gave this one as an extra homework to my friends class.. :E |
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Ekaterin Moderator on this forum Last page view: 5772 days, 19 hours, 26 minutes and 52 seconds ago. |
You ask "Which door would the other guy say leads to hell?" then take that door. If you spoke to the truthteller, he'll truthfully tell you that the liar would falsely indicate the door to heaven. If you spoke to the liar, he'll lie and say that the truthteller would point at the door to heaven. Actually, you don't need two people - you can just ask either one "If I were to ask you which door leads to heaven, what would you say?" Asking it as a hypothetical question means that the liar will lie about pointing to the wrong door, and the two lies cancel out. |
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Maastonakki Registered user A cute puppy Last page view: 5830 days, 17 hours and 54 minutes ago. |
As I am drunk (no women for me tonight as I'm writing here trying to forget my misery) I might want to say that I didn't get that one. A useless post indeed, but my ego needed a boost <3 (I'll think about that tomorrow when I'm less drunk :) |
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Caladriel Registered user ReGiStErEd UsEr Last page view: 4704 days, 8 hours, 13 minutes and 12 seconds ago. |
One that puzzled me as a kid: 3 business people go to a hotel. The room is $30, so they each give $10. Later, the manager realizes he misquoted the price. The room is only $25. The manager gives the bellhop $5 to return to the business people. The belhop realizes that $5 does not split eveny among 3 people, so he pockets $2, and give $1 back to each business person. Now then, in total, each business person has paid a total of $9, making $27 dollars. Add the $2 pocketted by the belhop and you account for $29. Where is the missing $1? |
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Morio Registered user Holy Champion of ADoM Last page view: 3905 days, 12 hours, 7 minutes and 32 seconds ago. |
this is a "funny" one assume that a=b a=b |multiply with b ab=b^2 |subtract a^2 ab-a^2=b^2-a^2 |then just make it look a bit nicer a(b-a)=(b-a)(b+a) |divide by (b-a) a=b+a and since b=a a=2a |divide by a 1=2 Spoiler
you are not actually allowed to divide by b-a since that is 0 "I don't know what World War 3 will be fought with, but I know World War 4 with be fought with sticks and stones." - Albert Einstein |
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tongHoAnh Unregistered user |
Math = logic About the doors thing: The guy picks 2 wrong doors instead of picking the correct one. The first one was a goat: 2/3 chance = 66.6% The second one shall be whatever: 1/2 chance = 50% The chance on obtaining BOTH the first and the second is (2/3)*(1/2) = 1/3 = 33.3% => The same as picking the right door at the beginning. |
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tongHoAnh Unregistered user |
math = logic The business people puzzle: Asumming the balance of the business people (BP), the hotel (HT) and the bellhop (BH) at the beginning is $0. After the business people give the money: BP: -$30 HT: $30 BH: $0 After the manager give money to the bellhop: BP: -$30 HT: $25 BH: $5 After the bellhop picks money and give the rest back to the business people: BP: -$27 HT: $25 BH: $2 The total sum is still 0. The trick is that people usually convert money into possitive number and forget that while HT and BH GAIN money, BP LOSE money, and the price is not $30 but $25. |
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Caladriel Registered user ReGiStErEd UsEr Last page view: 4704 days, 8 hours, 13 minutes and 12 seconds ago. |
tong: Spoiler Right. The $2 that the bellhop pocketted is part of the $27 which they have paid. Thus that $2 should not be added to the $27. If you start with the $27 paid by the business people, then the $2 should either be ignored, if you want to account for the originally $30, or subtracted if you want to account for the $25 held by the hotel manager. The trick was in the phrasing. The last paragraph should be: "Now then, in total, each business person has paid a total of $9, making $27 dollars. Subtract the $2 pocketted by the bellhop and you account for the $25 held by the hotel manager" or "Now then, in total, each business person has paid a total of $9, making $27 dollars. Add the $3 returned by the bellhop and you account for the original $30" [Edited 1 time, last edit on 2/17/2005 at 14:46 (GMT -5) by Caladriel] |
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raven1 Unregistered user |
geez how rude, NO TIP |
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raven1 Unregistered user |
lotta people worked |