## bean bag win

**A** quick riddle from The Riddler, where a multiple step game sees a probability of a 3 point increase of .4 and a probability of a 1 point increase of .3 with a first strategy (A), versus a probability of a 3 point increase of .4 and a probability of a 1 point increase of .3 with a second strategy (B), and a sure miss third strategy (C). The goal is to optimise the probability of hitting exactly 3 points after 4 steps.

The optimal strategy is to follow A while the score is zero, C when the score is 3, and B otherwise. The corresponding winning probability is 0.8548, as checked by the following code

win=function(n=1,s=0){ if(n==4)return((s==3)+.4*(!s)+.8*(s==2)) else{return(max(c( .4*win(n+1,s+3)+.3*win(n+1,s+1)+.3*win(n+1,s), .1*win(n+1,s+3)+.8*win(n+1,s+1)+.1*win(n+1,s), win(n+1,s))))}}

May 19, 2021 at 8:13 am

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