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extreme


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deff
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x - y = 50 x + 5y = 125
x = 50 + y
(50 + y) + 5y = 125 6y = 75 y = 12.5
12.5 steps? might be wrong with this
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deff
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Re: mathematical brain teaser thread [Re: deff]
#21967126 - 07/19/15 08:35 PM (8 years, 6 months ago) |
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actually nm, wrong with that ^
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Edited by deff (07/19/15 08:36 PM)
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deff
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Re: mathematical brain teaser thread [Re: deff]
#21967138 - 07/19/15 08:38 PM (8 years, 6 months ago) |
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x = number of steps y = additional number of steps due to movement in first trial
x - y = 50 x + 1/5y = 125
x = 50 + y
6/5y = 75
y = 62.5
x = 112.5 steps
probably not right since it comes out with a half step :/
edit: nm this is wrong too :/
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Edited by deff (07/19/15 08:43 PM)
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DividedQuantum
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Re: mathematical brain teaser thread [Re: deff]
#21967157 - 07/19/15 08:43 PM (8 years, 6 months ago) |
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Good guess but wrong. :/
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deff
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125 / 5 = 25
therefore it took half as long to go up as down
x - y = 50 x + 0.5y = 125
x = 50 + y
1.5y = 75
y = 50
x = 100
answer : 100 steps
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DividedQuantum
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Re: mathematical brain teaser thread [Re: deff]
#21967254 - 07/19/15 09:01 PM (8 years, 6 months ago) |
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DividedQuantum
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Official solution:
Let n be the number of steps visible when the escalator is not moving, and let a unit of time be the time it takes the professor to walk down one step. If he walks down the down-moving escalator in 50 steps, then n - 50 steps have gone out of sight in 50 units of time. It takes him 125 steps to run up the same escalator, taking five steps to every one step before. In this trip, 125 - n steps have gone out of sight in 125/5, or 25 units of time. Since the escalator can be presumed to run at constant speed, we have the following linear equation that readily yields a value for n of 100 steps:
(n - 50)/50 = (125 - n)/25
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DividedQuantum
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PROBLEM #18
Quote:
A. A fish weighs twenty pounds plus half its own weight. How much does it weigh?
B. If someone says to you, "I'll bet you a dollar that if you give me five dollars I'll give you a hundred dollars in exchange," would that be a good bet to take? Why or why not?
For competitive purposes, please post only if you have solved both problems.
Thank you.
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deff
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a - fish weighs forty pounds
b - yes good bet - he gives you five dollars, you don't give him 100 dollars and lose the bet, owing him one dollar, coming out 4 dollars ahead

edit: misread part b - good bet for the person making the bet, bad bet for you being offered the bet
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Edited by deff (07/19/15 09:17 PM)
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DividedQuantum
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Re: mathematical brain teaser thread [Re: deff]
#21967322 - 07/19/15 09:17 PM (8 years, 6 months ago) |
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DividedQuantum
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Re: mathematical brain teaser thread [Re: deff] 1
#21967333 - 07/19/15 09:19 PM (8 years, 6 months ago) |
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I knew what you meant.
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extreme


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Quote:
DividedQuantum said: Without further ado:
Quote:
Two girls were born on the same day in the same year to the same parents, yet they were not twins. Explain.
Just wondering, since word problems have some room open for interpretation (sometimes) since you didn't say the same month one could be born say, January 1st 2014, and the other November 1st 2014, right?
That probably isn't what the question means by "same day" but technically it is correct in a literal sense yea? Also if the third kid of triplets ends up dying, are the two remaining still triplets, or twins? Also of course quadruplets etc work 
Am I adding philosophy to these questions or do I just sound like an idiot? 
I'm gonna post a question if that's OK, I'll call it "bonus question" not to interfere with DQ's questions. Feel free to ignore it if it isn't apart of the rules for this thread. Sorry if it has already been posted :/
Quote:
Magician M1, calls an audience on stage who pulls random 5 cards from the deck.
M1 gives one card back to the guy from the audience; and lays out other 4 cards face-up and side-by-side on the table.
The Magician M2 comes and looks at the 4 open cards and is able to name the 5th card. How?
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Sun King



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Re: mathematical brain teaser thread [Re: extreme]
#21969841 - 07/20/15 09:08 AM (8 years, 6 months ago) |
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Witchcraft?
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DividedQuantum
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Re: mathematical brain teaser thread [Re: extreme]
#21970179 - 07/20/15 10:47 AM (8 years, 6 months ago) |
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Quote:
extreme said:
Quote:
DividedQuantum said: Without further ado:
Quote:
Two girls were born on the same day in the same year to the same parents, yet they were not twins. Explain.
Just wondering, since word problems have some room open for interpretation (sometimes) since you didn't say the same month one could be born say, January 1st 2014, and the other November 1st 2014, right?
That probably isn't what the question means by "same day" but technically it is correct in a literal sense yea? Also if the third kid of triplets ends up dying, are the two remaining still triplets, or twins? Also of course quadruplets etc work 
Am I adding philosophy to these questions or do I just sound like an idiot? 
I'm gonna post a question if that's OK, I'll call it "bonus question" not to interfere with DQ's questions. Feel free to ignore it if it isn't apart of the rules for this thread. Sorry if it has already been posted :/
Quote:
Magician M1, calls an audience on stage who pulls random 5 cards from the deck.
M1 gives one card back to the guy from the audience; and lays out other 4 cards face-up and side-by-side on the table.
The Magician M2 comes and looks at the 4 open cards and is able to name the 5th card. How?
Please do not get philosophical about the problems. There may occasionally appear to be room for interpretation, but just treat the problems as it is clear they are meant to be treated. Same day means same date here. There is not much ambiguity for the most part, anyway.
And I think your bonus question is perfectly acceptable.
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extreme


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Re: mathematical brain teaser thread [Re: Sun King]
#21970222 - 07/20/15 11:03 AM (8 years, 6 months ago) |
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Quote:
Sun King said: Witchcraft?
INCORRECT try again. PS it isn't "magic" either 
@ DQ - copy that. The first time I read it over I saw it the way most people did, but after thinking for a minute I started seeing holes in it, so to speak. But yea I dig. In an alternate universe the answer to my problem could very well be magic, maybe.
But not in this universe. You can post a question too if you have one mine is only bonus question.
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ballsalsa
Universally Loathed and Reviled



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Quote:
DividedQuantum said: PROBLEM #13
Quote:
If you happen to meet two of the Jones sisters (this assumes that the two are random selections from the set of all the Jones sisters), it is an exactly even-money bet that both girls will be blue eyed. What is your best guess as to the total number of blue-eyed Jones sisters?
all the jones sisters? you mean just from a singles jones family right? not all possible jones sisters?(i.e. 2 sisters from jones family A, 4 sisters from jones family B, 7 sisters from jones family C, etc. all of which could be classified in aggregate as jones sisters)
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DividedQuantum
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Re: mathematical brain teaser thread [Re: ballsalsa]
#21970337 - 07/20/15 11:43 AM (8 years, 6 months ago) |
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Yes, from the same set of sisters. Stop it.
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DividedQuantum
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PROBLEM #19:
Quote:
My wife and I recently attended a party at which there were four other married couples. Various handshakes took place. No one shook hands with himself (or herself) or with his (or her) spouse and no one shook hands with the same person more than once.
After all the handshakes were over I asked each person, including my wife, how many hands he (or she) had shaken. To my surprise each gave a different answer. How many hands did my wife shake?
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secondorder
Amanda Hug'n'kiss



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Can one person shake both of another person's hands at once?
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