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by rcyeh
January 28th, 2009, 3:12 am
Forum: Brainteaser Forum
Topic: Who Gets The Prize?
Replies: 25
Views: 52729

Who Gets The Prize?

<t>It's clear in vxs's case --- where the winner was the submission closest to 75% of the average --- whoever picked 100 was not expecting to win. In fact, I'd guess that everyone who picked above 40 did not understand the problem (or did not care about winning, which is the same thing). When I was ...
by rcyeh
January 28th, 2009, 1:29 am
Forum: Brainteaser Forum
Topic: The chairlift
Replies: 2
Views: 44364

The chairlift

<t>This reminds me of queuing problems in operations research, but I don't see an arrival rate.Suppose the slope took 1 second to ski down; then groups would spend most of the time in line. Suppose the slope took 30 minutes to ski down, and the bar service is slow; then usually, there would be nobod...
by rcyeh
November 8th, 2007, 2:52 pm
Forum: Brainteaser Forum
Topic: A world series puzzle
Replies: 13
Views: 72146

A world series puzzle

I agree. I drew out the same tree but made a mistake.
by rcyeh
November 8th, 2007, 2:37 pm
Forum: Brainteaser Forum
Topic: Constant Volatility Vs Normally drawn volatility
Replies: 5
Views: 68917

Constant Volatility Vs Normally drawn volatility

<t>Are you saying that in both cases the volatility would be constant during the life of the option, but in one case the volatility is known and in the other case, we are finding the expected price of the option given that the volatility is from a distribution centered at the known value?If so, I wo...
by rcyeh
November 8th, 2007, 2:20 pm
Forum: Brainteaser Forum
Topic: Length of train
Replies: 12
Views: 66927

Length of train

Maximum Likelihood Estimation is described in Paul Wilmott Introduces Quantitative Finance (2nd ed, page 211); he argues that n = 10 would maximize the probability of your having jumped onto car #10.
by rcyeh
November 5th, 2007, 4:27 am
Forum: Brainteaser Forum
Topic: what is bigger e^pi or pi^e?
Replies: 9
Views: 66609

what is bigger e^pi or pi^e?

<t>Hmm. Well, suppose x and y are real, and say f = exp(x) > 0 and g = exp(y) > 0. Then we are comparing 0.5*(f+g) [?] 0.5*f*g <=> 1/f + 1/g [?] 1.The left-hand side is bigger when f and g (implying x and y) differ by a large-enough margin: f/g > f-1 or g/f > g-1.The lhs is always bigger when f <= 1...
by rcyeh
October 30th, 2007, 4:49 pm
Forum: Brainteaser Forum
Topic: Length of train
Replies: 12
Views: 66927

Length of train

Is this related to < http://www.nytimes.com/2007/07/17/science/17tier.html >? "[The Copernican Principle] allows you to make predictions when you don't have any other information." Speaking of which, what's a train?
by rcyeh
October 30th, 2007, 4:36 pm
Forum: Brainteaser Forum
Topic: A world series puzzle
Replies: 13
Views: 72146

A world series puzzle

<t>$18.75, assuming even odds and bets only for your team.I had to draw out the tree, starting with game 7, where each team has 3 wins and 3 losses: if odds are even, you must start with zero dollars and bet exactly $100 on that last game. This implies that prior to game six, you had either +$50 (if...