reinout-g

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Usernamereinout-g
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 #17
avatar+2353 
+11
Melody:

Hard one (I'm curious to see whether anyone can find a different strategy than I found.) :

Steve again wants to play a game with you but you need $2 for each time you want to play.
Now, each time you play the game, Steve has the computer print 100 blank cards with 100 random different integers.
After that you can flip the cards for as long as you like until you choose to stop flipping. If your last card flipped is the highest card in the deck you will win $10.

Think of a strategy where you expect to win money in this game.
Hint: The cards you previously flipped can give you some kind of information.
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Alright then. I am assuming that I can only go through the 100 cards once.
I'll split the deck into 2deck of 50 cards each.
I'll go through the first 50 cards and note the highest integer.
Then I will stop at the 1st integer higher than this one in the second 50 cards.
If there are non higher then, I would have lost already.

The chance of success is not particularly high but it is better than no strategy at all.
Have you got a better idea reinout-g?



Actually your strategy is the same as I had, and the odds will win you money.

The strategy will pay off when the second-highest card of the 100 is in the first 50 cards and the highest card is in the last 50 cards.

Now there are four (almost) equally alike situations
Both the second highest card and the highest card are in the last deck - lose (at least, most of the times)
Both the second highest card and the highest card are in the first deck - lose (you won't find a value higher than the highest card)
The second highest card is in the last deck and the highest is in the first deck - lose (you won't find a value higher than the highest card)
The second highest card is in the first deck and the highest is in the second deck - win

So your chances of winning are a little over 25% (given that you might also stumble upon the highest card when you for example have the third highest card set as your value)
Now the game costs $2 to play and the winning are $10. So the expected value per game is at least E(X) = -2*0.75 + 10*0.25 = -1.50 + 2.50 = $1.
Mar 4, 2014
 #6
avatar+2353 
0
reinout-g:

maybe people would consider this cheating but nobody said we could only use basic computations.
Here we go...

0= 1*(9-9)*4... ........................ Grmal
1 = 1994
2 = -1-9/9 +4.. .........................Melody
3 = -1-9 +9+4.. ....................... Melody
4 = -1+9/9+4.... .........................Melody
5 = ceiling [ (-1+9) / 9] + 4... .....Melody (I am cheating a bit here, ceiling means find the answer and round it up to the nearest whole number)
5 = 1+9-9+4...........................Demogorgon
6 = 1+4+9/9...........................Demogorgon
7 = 19-(9+4)...........................Demogorgon
8 = sqrt(9)*sqrt(9)-14
9 = 9*149
10 = sqrt(9)*sqrt(9)+14
11 = 9+sqrt(4)*14
12 = 9+sqrt(4)+14
13 = 9+9-(1+4)...........................Demogorgon
14 = (9+9-4)*1...........................Demogorgon
15 = 1+9+9-4...........................Demogorgon
16 = 9+9-sqrt(4)*1
17 = 9*4-19...........................Demogorgon
18 = 9+9*14
19 = 9+9+14
20 = 9+9+sqrt(4)*1
21 = 9-1+9+4...........................Demogorgon
22 = (9+9+4)*1...........................Demogorgon
23 = 9+9+4+1...........................Demogorgon
24 = (9-14)*sqrt(9)
25 = (99+1)/4...........................Demogorgon
26 = -1-9+9*4 ... .......................Melody
26 = 9*4-(1+9)...........................Demogorgon
27 = 9*4*1-9...........................Demogorgon
28 = 9*4+1-9...........................Demogorgon

29 = (9+1)*sqrt(4)+9

Anyone care to join in using some more computations?


30 = 49-19...........................Demogorgon

36 = 9(9-4-1)...........................Demogorgon
37 =

39 = 49-(9+1)...........................Demogorgon

40 = (49-9)*1...........................Demogorgon
41 = 4(9-1)+9...........................Demogorgon
42 = 91-49...........................Demogorgon

44 = 9(9-4)-1...........................Demogorgon
45 = 9*4*1+9...........................Demogorgon
46 = 9*4+1+9...........................Demogorgon

50 = (9+1)(9-4)...........................Demogorgon

54 = 9(9-4+1)...........................Demogorgon

57 = 9-1+49...........................Demogorgon
58 = 99-41...........................Demogorgon

67 = 9*9-14...........................Demogorgon
68 = 9(9-1)-4...........................Demogorgon

75 = 94-19...........................Demogorgon
76 = 9*9-1-4...........................Demogorgon
77 = 9*9*1-4...........................Demogorgon
78 = 9*9+1-4...........................Demogorgon

84 = 9*9-1+4...........................Demogorgon
85 = 9*9*1+4...........................Demogorgon
86 =9*9+1+4...........................Demogorgon

94 = 99-4-1...........................Demogorgon
95 = 9*9+14...........................Demogorgon
96 = 91-4+9...........................Demogorgon

Mar 3, 2014