On-Sets Operations

Some students have trouble remembering which operation gives what. Here’s a set of helpful reminders:

Prime names the complement of a set. In other words, it is the cards that are NOT in a particular set. B’ (“blue prime”) gives the cards that are NOT Blue.

Intersection looks for cards that have both Set1 AND Set2. R Ω B names the cards with both Red AND Blue on them. Try remembering it as the AΩD (“AND”) cube.

The union of two sets contains any cards that fall into either Set1 OR Set2. G U Y names all of the cards that have either Green OR Yellow on them. You only count a card once if it has both sets. It may not be grammatically correct, but you think of this as the OUR (“OR”) cube.

Set subtraction is not too far off from the more common algebraic subtraction. Using the minus sign, you are looking for the cards in Set1 WITHOUT Set2. R – G (“red minus green”) names the set of Red cards WITHOUT Green on them. This is the same set as R Ω G’ (“red and green prime”).

Now, you know all of the ways to recall the meaning of each operation symbol.