Question

Bill, George, and Ross, in order, roll a die. The first one to roll an even number wins and the game is ended. What is the probability that Bill will win the game?

Answer 1

Answer:$0.5714\frac{1}{15}$

Step-by-step explanation:

Given that Bill, George, and Ross, in order, roll a die.

The first one to roll an even number wins and the game is ended.

Since Bill starts the game he can win by throwing even number or lose by throwing odd number

P(win) = 0.5, otherwise, the die will go to George.  For Bill to win, both George and Ross should throw an odd number so that Bill again gets the chance with game non ending.

Thus we have Prob of Bill winning =P of Bill winning in I throw +P of Bill winning in his II chance of throw +....infinitely

To get back the dice once he loses probability

= p both throws odd = $0.5(0.5) = 0.25$

Thus Prob for Bill winning

= $0.5+0.25(0.5)^2+0.25(0.5)^3(0.25)+...$

This is an infinite geometric series with I term 0.5 and common ratio 0.125<1

Sum = $\frac{a}{1-r} =\frac{0.5}{1-0.125} =0.5714$