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 Set Me Up (Posted on 2004-02-10)
To demonstrate set union and intersection to her class, Mrs. Putnam asked for three students to each write down a set of numbers.

After they had done so, she looked at their sets and told the class, "the union of these three sets is the first ten counting numbers, but their intersection is empty!"

How many triples (A, B, C) of sets are there such that

A U B U C = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
and
A ∩ B ∩ C = {} ?

 See The Solution Submitted by DJ Rating: 4.3636 (11 votes)

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 re: solution | Comment 7 of 31 |
(In reply to solution by Charlie)

Charlie
a. For ordered triples: you have to carefully discount the empty sets: each student was asked to write numbers and not display wiseguyness ,
b.For unordered triples: you have to be careful not to count things twice- choices with one empty set were ignored by you.

 Posted by Ady TZIDON on 2004-02-10 10:55:19

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