
David B. answered 08/23/21
Math and Statistics need not be scary
This is actually easier to calculate than it looks like at first.
I will assume the participants are given PAINT guns and are properly dressed with safety gear and are at proscribed safe distances. Violence and or killing , even in hypothetical situations is not to be condoned or even considered. This is a violence free site.
For A to win all competitors have to be eliminated (hit by a paint ball) . There are several probability branches that lead to this.
1) A hits B (round1) , A hits C (round2), A hits D (round3) after C misses D in round 1, and D misses A in round 1 and 2
2) A hits B (round1) , A hits C (round2) after C hits D in round 1
3) A misses B (round1), A hits B (round 2) , A hits D ( round 3) after D misses A in round 1 and 2
4) A misses B (round1), A misses B (round 2) , A hits B (round3) after D misses A in round 1
p(1) = .3 *( .3*(1-.7))*(.3*(1-.7)*(1-.5)) : .00125
p(2) = .3*(.3*.5). : .045
p(3) = .7 * (.7 *(1-.7))*(.3*(1-.7)). : .01323
p(4) = .7*(.7*.3)*.3. : .0441
Total chances to win = .10358