Question

有5人站成一圈传球每人只能传给他左右的人,首先由A传.问十次后球回到A的概率

Answer 1

经十次后球又回到A的概率为：

C(10,0)*(1/2)^0*(1/2)^(10-0)+C(10,5)*(1/2)^5*(1/2)^(10-5)+C(10,10)*(1/2)^10*(1/2)^(10-10)

=(C(10,0)+C(10,5)+C(10,10)))*(1/2)^10

=(1+252+1)/2^10

=254/1024

=127/512