# If you need help with Math homework post here.

Discussion in 'BlackHat Lounge' started by alonski, Jan 13, 2009.

1. ### alonskiJunior Member

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Hi I am in 12th grade and have a great knowledge of Math. I am in the highest level math possible in my school and think that I do pretty well. So post questions here and I will answer them to the best of my ability with explanations. Please if it is beyond high school don't post this. I do have a life and can't spend my whole day solving math problems =)

2. ### dosephRegistered Member

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does 0.999... = 1 ?

3. ### coreygeerBANNEDBANNED

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Three men are travelling and get tired, so they decide to spend the night at a nearby inn. When they go to the front desk, the innkeeper charges them \$30, (\$10 each), and the three men go into their rooms and go to sleep. Then the innkeeper realizes that he was only supposed to charge the men \$25 total, so he gives \$5 to the bellboy to give to the men. But on the way to the men's rooms, the bellboy thinks to himself, "Hey, I've been so good, I deserve some money." So he keeps \$2 and gives the remaining \$3 to the men. Because they each get \$1 back, they paid \$9 instead of \$10 each. But 3 x 9 = 27. But \$30 - the taken \$2 = \$28. Where is the missing dollar?

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We unravel this confusion by recognizing that there is no reason to add \$2 to \$27. By adding \$2 to \$27, the \$2 is counted twice and the \$3 returned to the guests is not counted at all.

What helps make this even more confusing is that it's only off by a single dollar. For some reason, a error of +/- one is more difficult to track down than a larger sum, perhaps because it's so close to the correct total.

This problem provides a means to understand how misdirection, and irrelevant facts and questions, can foil clear analysis. Additionally, the tools used to resolve this paradox are used in the analysis of a wide range of financial and scientific areas.

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5. ### aardanyulBANNEDBANNED

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i have a math tutor. its called a calculator.

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6. ### Mp3MageBANNEDBANNED

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That's crazy... I had to read that a couple of times to finally get it lol.

I use microsoft calculator to do derivatives and quantum physics.

:usa:

7. ### secretboy08Jr. VIPJr. VIP

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if you could have met me before my maths exam.
i had fourier series,matrices,z transforms and what not.

i will definitely going to fail because i was busy making money.LOL

8. ### bluebookNewbie

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They were supposed to pay \$8.33 (\$25/3) each, not 9.

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Strike one.

10. ### alonskiJunior Member

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The bellboy kept \$2... Anyways doseph 0.999 repeating 9s does equal 1.
This can be explained here: http://en.wikipedia.org/wiki/0.999...#Proofs
My favorite explanation is that 1/3 = 0.3333 repeating. 1/3+1/3+1/3 = 1
0.3333 repeating + 0.3333 repeating + 0.3333 repeating = 0.9999 repeating
This concludes that 0.9999 repeating = 1.

11. ### EntrepreneurBANNEDBANNED

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There's a game show where 3 doors are in front of the contestant. Behind 2 doors are sheep, behind the other, a car.

The host asks the contestant to pick a door.

The contestant picks door 3, and then the host, knowing exactly what is behind each door, opens door 1, to reveal a sheep. The host then asks the contestant if he'd like to swap to door 2.

Should the contestant swap doors and why?

(I've changed some small aspects of the question to make Googling the answer harder, so no one give away the name of the problem if they know the answer please!)

12. ### lukeevansJunior Member

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Well There is 6 possible options

If you choose to stick with the door you pick
Pick winner win
Pick loser1 lose
Pick loser2 lose

If you switch
Pick winner lose
Pick loser1 win
Pick loser2 win

13. ### bluebookNewbie

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If I recall from high school, you SHOULD change your answer because you originally had 1/3 chance of getting it right. With 1 door revealed, you now have a 2/3 chance of getting it right.

14. ### lukeevansJunior Member

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Originally you had a 1/3 chance at winning and a 2/3 chance of picking the losing door. Which means there was a greater chance that you picked the loser from the get go. The host eliminated one of the doors as a winner, so that means you basically flipped the odds, the host in a way gave you two winning doors.

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math HW FTW!

16. ### GeetfauxSuper ModeratorStaff MemberModerator

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From the film 21 eh? variable change ftw

17. ### EntrepreneurBANNEDBANNED

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Haven't seen it, but it gets mentioned alot. It's known as The Monty Hall Paradox and i first came across it in a book called, The Curious Incident of The Dog in the Nighttime.

And for those that care, or still think it's 50/50, the easiest explanation is to imagine there's 100 doors, the contestant picks one and the host opens 98 doors revealling sheep....

18. ### shylessonPower Member

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That is so hot. So hot for real. I LOVE it! ~(* *)~ Especially that last paragraph.......I love a mind!

19. ### seamusmcaffreyRegistered Member

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black hat world was slightly my downfall on exams this past semester too.

and yeah, i'm a senior engr physics major- so to YOU, alonski- i'll help you out when you get lost haha.

20. ### secretboy08Jr. VIPJr. VIP

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cool to see another engineering student here.
well i am not a major.i am in electronics and telecom engineering degree.