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by arkol
October 26th, 2009, 11:57 am
Forum: Brainteaser Forum
Topic: Ants On A Line
Replies: 6
Views: 35488

Ants On A Line

by arkol
October 26th, 2009, 11:54 am
Forum: Brainteaser Forum
Topic: Ants On A Line
Replies: 6
Views: 35488

Ants On A Line

take common speed v(t) integrable function on 0,+infinity (e.g -t as in the first case or -10*t*cos(t) )let V(t) = integral_0^t v(s) dslet f_n = abs(V(t) + (n+1)/2)) + (n-1)/2f_i-1 = abs(f_i - i/2)+(i-2)/2 for i = n .. 2are the trajectories for ants n..1 take opposites for ants -1..-n
by arkol
October 12th, 2009, 8:57 am
Forum: Brainteaser Forum
Topic: Prob Question
Replies: 16
Views: 39089

Prob Question

<t>MatthewM, basically I did the same eliminating some states as below:this is the version without counting the draws as win for player1:p = 1/4 * T H pm1/4 * T T p1/4 * H T pp1/16 * HH HT 11/16 * HH HH 11/16 * HT HT p1/64 * HTH HHH 01/64 * HTH HHT pp1/64 * HTT HHH 01/64 * HTT HHT pp=pp/4+pm/4+p/4+1...
by arkol
October 11th, 2009, 1:30 pm
Forum: Brainteaser Forum
Topic: Prob Question
Replies: 16
Views: 39089

Prob Question

<t>pm is basically the probability of player1 winning the game if in the first round p1 got a T and p2 got an h (so p1 had a bad start and has slightly less chance to win )the problem is to find the probability of player1 getting hh before player2 gets hhh. for me the game stops as soon as player1 g...
by arkol
October 10th, 2009, 9:26 am
Forum: Brainteaser Forum
Topic: Prob Question
Replies: 16
Views: 39089

Prob Question

<t>p = proba of winning for player 1pp = proba of winning for player 1 if starting with TH,.T (e.g. H,T or THTH,TTTT etc)pm = proba of winnign for palyer 1 if starting with .T,TH (e.g. T,H or THTHT,HTTTH etc)Equation pp=1/2+pm/4+p/4,pm=pp/4+p/4+p/8+pp/16+2/16,p=pp/4+pm/4+p/4+1/8+p/16+pp/64+p/64 solv...
by arkol
September 22nd, 2009, 3:37 pm
Forum: Brainteaser Forum
Topic: Is it true!!!!
Replies: 6
Views: 36594

Is it true!!!!

<t>givenstudent A writes astudent B writes bteacher writes smin < smaxproblem: find sum sanswersA1:if a > smin => s = smax qedelse a < sminB1:if b > smin => s = smax qedelse b < sminA2:from B1: a + b < smin + aif smax > smin + a => s = smin qedelse a > smax - sminB2:from A1: a + b < smin + bif smax ...
by arkol
August 11th, 2009, 4:37 pm
Forum: Brainteaser Forum
Topic: The isolated village
Replies: 24
Views: 42276

The isolated village

<t>the problem is more clear if you put it likethe guy who knows kills himself only at midnight and the others discover the dead in the morning.put yourself in their place:if you see 0 whites you know you are the one and you kill yourself at midnight 1. if you see 1 white and no one dies at 1 then y...
by arkol
June 5th, 2009, 10:58 am
Forum: Brainteaser Forum
Topic: Ian Stewart's problems in Prospect magazine
Replies: 2
Views: 39902

Ian Stewart's problems in Prospect magazine

(1,1),(1,2),(4,1)
by arkol
March 9th, 2009, 10:20 am
Forum: Brainteaser Forum
Topic: Parabola's Interesting (& Useful) Property
Replies: 2
Views: 43093

Parabola's Interesting (& Useful) Property

say (0,x_0) is the focal, by analytic geometry (and maybe a bit of trigonometry) you see that a solution should verify something likeand if you fix an initial condition outside the origin then this should have a unique solution on a neighbourhood of it.
by arkol
January 19th, 2009, 11:09 am
Forum: Brainteaser Forum
Topic: chess tournament
Replies: 2
Views: 44954

chess tournament

4 beats 5:last four would get 6 points at least as the sum of the matches done just between them.i.e second has at least 6 points. cannot be 7 or 6.5 as 1st is strictly greater than 2nd. so it is 6. i.e last 4 has lost all the games against first 4. i.e. 5 lost to 4.
by arkol
December 29th, 2008, 7:08 pm
Forum: Brainteaser Forum
Topic: hanging a picture
Replies: 3
Views: 46106

hanging a picture

<t>a is the path clockwise around the nail Aa' is the path counterclockwise around the nail Ab is the path clockwise around the nail Bb' is the path counterclockwise around the nail Be is elementary path hanging out in the airnote that aa' = a'a = ebb' = b'b = eyou can represent a way of hanging by ...
by arkol
December 17th, 2008, 12:16 pm
Forum: Brainteaser Forum
Topic: Hexagon
Replies: 6
Views: 46839

Hexagon

starter needs max 4 steps to get a triangle and it works for 5 points as well
by arkol
December 9th, 2008, 3:33 pm
Forum: Brainteaser Forum
Topic: 27 cubes
Replies: 7
Views: 49476

27 cubes

you can free the central cube in 5 cuts: cut the on diagonal to 2 identical pieces than free the 4 remaining faces of the central half cubes simultanously at 4 cuts and put back the halves togather..as you say there is a way to do it at 6 but there might still be a way to do it at 5...
by arkol
December 9th, 2008, 10:24 am
Forum: Brainteaser Forum
Topic: 27 cubes
Replies: 7
Views: 49476

27 cubes

5.each cut can be applied to all existing pieces by stacking all on top of the other and going through all at once. this multiplies then number of pieces by 2. as 27 <2^5 you need only 5 cuts