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 = {} ?
(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.
Please comment upon my solution
ady
re: solution
