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A catalog contains 10 itmes. Two people, A and B each select 3 items from the catalog independently. What is the expected value of the number of items A and B ordered.

My attempt:

Let A chose any 3 items. The probability that B

Chose 1 similar item is 3/10

Chose 2 of the same items = 3/10*2/9

Chose 3 of the same items = 3/10*2/9*1/8

And so the expected value is 1*(3/10) +2*(3/10*2/9) + 3*(3/10*2/9*1/8) = 11/24

But he awnsers page sais it is 0.9

I don't really know what I'm doing wrong

Guidance needed :)

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# Homework Help: Expected value question

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