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RE: Riddles, brain puzzles and mathematical problems - Froge - 12-09-2012

Yes;

@BAndrew: It's the easiest subject in math imo and doesn't really require any teaching.

RE: Riddles, brain puzzles and mathematical problems - BAndrew - 12-09-2012

(12-09-2012, 10:44 PM)Chronofox Wrote: Yes;

@BAndrew: It's the easiest subject in math imo and doesn't really require any teaching.
We are supposed to learn about this subject next year so I am serious when I say that I don't have any idea of how it works. Anyway you mentioned there is might something that we should know about stats 101. What is it?

RE: Riddles, brain puzzles and mathematical problems - Froge - 12-09-2012

Knowing Stats 101 would simplify the question, but it's completely doable without it.

RE: Riddles, brain puzzles and mathematical problems - BAndrew - 12-09-2012

(12-09-2012, 10:54 PM)Chronofox Wrote: Knowing Stats 101 would simplify the question, but it's completely doable without it.
Oh, OK then.

RE: Riddles, brain puzzles and mathematical problems - Bridge - 12-09-2012

$5.0475?

RE: Riddles, brain puzzles and mathematical problems - Froge - 12-09-2012

nope

By the way, what is your methodology for the 2nd part?

RE: Riddles, brain puzzles and mathematical problems - Bridge - 12-09-2012

See my notes I posted a while back, titled 2nd.

RE: Riddles, brain puzzles and mathematical problems - Froge - 12-09-2012

Yeah, that's wrong too.

The 2nd part requires a certain trick, it's a bit hard to see.

RE: Riddles, brain puzzles and mathematical problems - Bridge - 12-09-2012

Count me out. As I said before, I have a math final tomorrow that I need to study for. While this has been a good exercise I can't waste any more time on it.

RE: Riddles, brain puzzles and mathematical problems - Froge - 12-11-2012

Ok, it's a bad puzzle. It takes way too long to do without knowledge of statistics, and even then comes down to an extraordinary amount of grindwork, unless you have a graphics calculator.

Spoiler below!
Part 1 is just finding out all the different possible outcomes of one round. The easy way to do this is with binomial probabilities.

ALIAS Probability generator: (0.5 + 0.5)^3
Kman Probability generator: (0.6 + 0.4)^2

A-win: 3-2, 3-1, 3-0, 2-1, 2-0, 1-0

= (0.5)^3 * (0.6)^2 + 0.5^3 * 2 * (0.6)(0.4) + 0.5^3 * (0.4)^2 + 3 * 0.5^3 * 2 * 0.6 * 0.4 + 3 * 0.5^3 * 0.4^2 + 3 * 0.5^3 * 0.4^2
= 0.425

K-win: 1-2, 0-2, 0-1

= 3 * 0.5^3 * 0.6^2 + 0.5^3 * 0.6^2 + 0.5^3 * 2 * 0.6 * 0.4
= 0.24

Tie: 0-0, 1-1, 2-2

= 0.5^3 * 0.4^2 + 3 * 0.5^3 * 2 * 0.4 * 0.6 + 3 * 0.5^3 * 0.6^2
= 0.335

Check: 0.335 + 0.425 + 0.24 = 1, so it's correct.

Alias E(X) = 6 * 0.425 - 10 * 0.24 - 2 * 0.335
= -$2.08

But he gets $5 from Kman so ALIAS is actually at $5 - $2.08 = $2.92

SECOND HALF:

Redo all of the above binomial probabilities with Kman's values fixed to fair coins (I had to resort to a calculator at this point) and you should get:

P(ALIAS wins) = 1/2
P(Kman wins) = 3/16
P(Tie) = 5/16

Probability of ALIAS winning round 1: P(ALIAS wins) = 1/2

Probability of ALIAS winning round 2: P(Tie) * P(ALIAS wins) = (5/16) * (1/2)

Probability of ALIAS winning round 3: 2 * P(Tie) * P(ALIAS wins) = (5/16)^2 * (1/2)

Probability of ALIAS winning round 4: 3 * P(Tie) * P(ALIAS wins) = (5/16)^3 * (1/2)

If this continues you should see that it's a geometric series with first term 1/2 and ratio of 5/16. Using the formula for summation of an infinite geometric series:

Sn = u1 / (1 - r)
= (1/2) / (1 - 5/16)
= 8/11

ALIAS E(X): 8/11 * $11 - 3/11 * $11 = $8 - $3 = $5

Adding $5 to his winnings from round one, $5 + $2.92 = $7.92.

ANSWER: $7.92

I'll give y'all another question to do as replacement for this one. This question doesn't require much knowledge of stats at all.

Horror Games


An interview with citizens of Chronoville gives us the following information:

>45% of the population has played Amnesia: The Dark Descent.

>x% of the population has played Silent Hill.

>If someone has not played Silent Hill, then the probability of them having played Amnesia is 3/7.

>If someone has played Silent Hill, then the probability of them having played Amnesia is 6/13.

One person is picked at random. What is the probability that they have not played Amnesia and Silent Hill? (This means that they can have played one of the games, or none of the games at all. Just as long as it's not both games)