Q11:
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1 2 3 4
The figure shown represents a board with 4 rows of pegs, and at the bottom of the board are 4 cells numbered 1 to 4. Whenever the ball shown passes through the opening between two adjacent pegs in the same row, it will hit the peg directly beneath the opening. The ball then has the probability 1/2 of passing through the opening immediately to the left of that peg and probability 1/2 of passing through the opening immediately to the right. What is the probability that when the ball passes through the first two pegs at the top it will end in Cell 2?
A. 1/16
B. 1/8
C. 1/4
D. 3/8
E. 1/2
Why the OA is D? I got B, please help. thanks
6.
O
X X
X X X
X X X X
X X X X X
M M M M
上图第一行"O"表一小球, 第2,3,4行的"X"表障碍物, 第6行表小槽. 小球从上落下,在第三行时
受到障碍物的阻止, 其向左或右的机率相等, 各占50%. 以下依然. 问最后球掉到第六行的第二个
M的机率? (3/8)
对每一行落到X的概率都表示出来，然后即可得出结论为3/8
