5944概率中等数值题medium

Two Unequal Prizes

题目

Each cereal box contains one prize: a common prize with probability $2/3$ and a rare prize with probability $1/3$ , independent across boxes. What is the expected number of boxes you must open to have collected both prizes?

解题计时

0:00

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你的答案

数值

boxes

只填写数值本身，单位 boxes 已固定在输入框右侧。