Question 1208678: What is the cardinality of set B?
B = {pi, e, {x, y, y} }
I see three items in set B.
I see pi, e, and another set containing elements x, y, and z
My answer is 3.
The cardinality is 3.
You say?
Answer by ikleyn(52903)   (Show Source):
You can put this solution on YOUR website! .
In your post, you write
"I see pi, e, and another set containing elements x, y, and z ".
I do not see it.
What I see is pi, e, and the list {x,y,y} in curved brackets,
which contradicts to the rules of presenting sets, since the element "y" is repeated twice.
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Comment from student: Inside set B is another set. Let's call the other set a smaller box.
It's like opening a box and finding a ball, glove and another box. We don't know what lies inside the smaller box.
So, when I open the bigger box, I see three items: ball, glove and smaller box.
So, the cardinality is 3.
NOTE: I MADE A TYPO. THE SET INSIDE SET B SHOULD HAVE ELEMENTS X, Y, AND Z NOT X, Y, AND Y.
WE DON'T REPEAT THE ELEMENTS IN A SET. YOU SAY?
My response: Correct.
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