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by timeds
May 14th, 2008, 9:44 am
Forum: Brainteaser Forum
Topic: How to price this voucher?
Replies: 5
Views: 55693

How to price this voucher?

<t>I would sell it for (probability I spend it in Legoland * 40) + (probability I spend it in tesco * 10) + (probability I put it in a drawer somewhere and forget about it for three years * 0)Time discount seems a little irrelevant - any spurious accuracy here is more than compensated for by very do...
by timeds
April 20th, 2008, 11:53 am
Forum: Brainteaser Forum
Topic: Square holes
Replies: 19
Views: 60920

Square holes

how about a cylinder (diameter = length) covered in sandpaper? Rotation would be parallel to surface
by timeds
April 8th, 2008, 10:16 pm
Forum: Off Topic
Topic: Cleaner than clean?
Replies: 150
Views: 74899

Cleaner than clean?

<t>Casual, vicious sexism, a discussion of how why strippers make good girlfriends ... inspired by schadenfreude over some politician using hookers. The bitterness is palpable. I don't think you're going to find that kind, beautiful girl who wants to marry you and "deserves loyalty when she is 50". ...
by timeds
April 2nd, 2008, 12:35 pm
Forum: Brainteaser Forum
Topic: two interview questions
Replies: 8
Views: 60909

two interview questions

<t>I think we all agree that the time value of money is equivalent to a positive riskless interest rate. Risk free rates are driven by at least two factors: opportunity cost of lending money, and inflation. If you have some money, you might be able to make it grow by investing wisely in the instrume...
by timeds
March 16th, 2008, 11:53 am
Forum: Brainteaser Forum
Topic: 2 goals? 3 goals?
Replies: 13
Views: 61218

2 goals? 3 goals?

Depends on the match ... spread betting and outright bets on the number of total goals is easily available from plenty of online bookies for most matches. If you can arbitrage your boss once in a while then the remaining problem is moral/tactical rather than mathematical ...
by timeds
February 2nd, 2008, 9:10 pm
Forum: Brainteaser Forum
Topic: Maximum permutations
Replies: 7
Views: 63301

Maximum permutations

<t>If you have a 'set of of operations' and you can continue to apply them in any order you like then, as long as you have more than one, you don't ever have to get back to the starting position (if operation E takes you back to the start then do E' instead) On the other hand you can't have a singe ...
by timeds
January 20th, 2008, 12:35 pm
Forum: Brainteaser Forum
Topic: Maximum permutations
Replies: 7
Views: 63301

Maximum permutations

<t>For n>2 an easy upper bound might be (n! / 2).The reason being that the set of permutations on n elements is a group (the symmetric group) and this has size n!. Since the order of any element divides the order of the group, m divides n!. For n > 2 this group is non-abelian and in particular non c...
by timeds
December 24th, 2007, 11:23 am
Forum: Brainteaser Forum
Topic: Length of train
Replies: 12
Views: 67416

Length of train

How about 19? On average you would expect as many carriages to be in front of yours as there are behind.
by timeds
December 12th, 2007, 8:05 am
Forum: Brainteaser Forum
Topic: A probably easy Combinatorics problem
Replies: 36
Views: 69929

A probably easy Combinatorics problem

<t>As I understood the question having only balls 1,3 in bucket 2 would not be an allowable solution. Effectively you go through the buckets one by one and decide how many balls to put in, i.e. if balls a, b are in buckets x,y then a > b implies x >= yThis applies to the second point as well. Once y...
by timeds
December 7th, 2007, 10:17 am
Forum: Brainteaser Forum
Topic: A probably easy Combinatorics problem
Replies: 36
Views: 69929

A probably easy Combinatorics problem

<t>Have an answer and can prove it - but sadly I can't see why it's equivalent to the earlier solution. I like n for balls and M for buckets ...So how may distinct ways are there to order n balls among M numbered buckets in the way described? For each instance, let k be the number of buckets that ha...
by timeds
July 23rd, 2007, 1:13 pm
Forum: Brainteaser Forum
Topic: climbing down a mountain
Replies: 8
Views: 71090

climbing down a mountain

Here's an easy one:You are at the top of a 200m cliff with a rope of 150m length. There is a tree at the top of the cliff and halfway down the cliff there is a small ledge with another tree. You can only attach your rope to the trees and not to the cliff.How to get down?
by timeds
June 20th, 2007, 9:55 am
Forum: Brainteaser Forum
Topic: an interview coin quesiton
Replies: 23
Views: 78791

an interview coin quesiton

<t>A = See N consecutive tails before (the first time) you see N consecutive headsB = See N consecutive heads before (the first time) you see N consecutive tailsso P(A) = P(B) and P(A and B) = 0You play the game (ie go along infinite sequence of heads, tails) until you see N consecutive heads, at wh...
by timeds
June 15th, 2007, 2:40 pm
Forum: Brainteaser Forum
Topic: an interview coin quesiton
Replies: 23
Views: 78791

an interview coin quesiton

surely probability of seeing 8 consecutive heads before you see 8 consecutive tails is equal to the probability that you see 8 consecutive tails before you see 8 consecutive heads.Since one must occur the probability is 50%.
by timeds
June 15th, 2007, 2:09 pm
Forum: Brainteaser Forum
Topic: A special die
Replies: 9
Views: 73004

A special die

Let the dice land showing side X and then side YChance that both are sixes = P(X is a six) * P(Y is a six given X is a six)The chance that side X is a six is 1/6The chance that side Y is a six given that X is a six is P(X=!Y)*P(Y=6) + P(X=Y) = (5/6)*(1/6) + (1/6) = 11/216 or about 5.093
by timeds
June 15th, 2007, 8:51 am
Forum: Brainteaser Forum
Topic: Parking Space Lottery
Replies: 3
Views: 71621

Parking Space Lottery

<t>OK first of all the problem is symmetric - in both cases the employees all have an equal probability of getting a parking space. Unless you could e.g. choose 10 spots very far away from the office and know that no-one else wants them (so then the second option is better) but it seems that you mea...
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