推 ting301:EX=1 ?? 12/28 22:06
推 lmvue:(10^3-9^3)/10^2 12/28 22:20
→ stevegood:感謝，我發現我誤會題目的意思了 12/29 10:04
1.A class has three students. They toether participate in 10 courses.
Each student has one favorite course. Let X be the number of courses
that are the favorite courses of at least one student. Suppose that a
student is equally likely to favor any of the 10 courses. Find E[X]=?
我算出來是3 可是答案好像不是(忘了)
希望高手解答瞜!
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