2.) suppose that my favorite number is 3 and I insist on betting on 3 in every g
ID: 3276439 • Letter: 2
Question
2.) suppose that my favorite number is 3 and I insist on betting on 3 in every game.
A.) if I play 5 games in a row, betting on 3 straight each time, what are the odds that I win at least once
B.) after playing 3 straight for several games and becoming depressed at my losses, I decide to try to win my money back. Since I also like the color red,I decide to place bets on both 3 straight and the color red. determine (by counting ) the odds that at least one of my bets wins in any given game. can the odds be calculated by using the formula, P (3,red)=P (3)+P (red)? explain
C.) the payout for a straight bet is 35 to 1 and the payout for a color bet is 1 to 1. why would someone make the bet described in (B.)? does it make more sense to be on both red and 2 straight (assuming that I can bring myself to bet straight on any number besides 3, of course)?
Explanation / Answer
2. In a roulette game there are 38 possible outcomes. If we decide to bet on a single number say '3' then the probability of winning in any single game is 1/38. If we decide to bet on a single colour either red or black then the probability of winning is 18/38
(A) It is given that five games were played in a row, betting straight on 3 each time.
Let X denote the number of wins in the 5 plays.
Then the probability of winning atleast once is given by P(X1) =1 - P(X=0).
Now, P(X=0)=P(Zero win in 5 plays) = 37/38 x 37/38 x 37/38 x 37/38 x 37/38 = 0.8752
So, P(X1) =1 - P(X=0)
P(X1) =1 - 0.8752
P(X1) =0.1248
(B) There are 18 cells cells which are coloured red. Additionally, the cell which is numbered 3 is also coloured red. So, here both the events intersect and the total number of favourable outcomes is 18.
So, probability of winning when a bet is placed on 3 straight and the colour red is 18/38
Since, the two events coincide as the cell 3 is also red in colour.
So, in other words P(Atleast one of the bets wins) = P(Either the number 3 comes or the colour red comes)
Since the event getting 3 is a subset of getting the colour red, we have
P(Atleast one of the bets wins) = P(The colour red comes)=18/38
P(Atleast one of the bets wins) = 0.47368
Now, it is seen that
P(red)=18/38 = 0.47368
P(3)=1/38 = 0.02632
P(3,red)= 18/38 = 0.47368
So, from the above we see that P(3,red) P(3)+P(red)
(C) Betting straight on 3 and the colour red together will increase the expected payout from the game. So, it might be considered to bet in a way as described in (B).
Yes, it will be better to bet on the colour red and the number 2 because the two events are exclusive (as the number 2 is black in colour). So, the number of favourable outcomes in this case will be 18+1=19.
And the probability of winning will be 19/38 = 0.5 which is more than before.
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