Unit 11 · Set Operations
Set Operations
Mathematics · Grade 7
What You Will Be Able To Do
∪Work out unions, intersections, differences and complements
🔤Recognise which operation a word problem is really asking for
➖Count a union without counting the overlap twice
🔍Solve survey problems: how many do only one, both, or neither
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Once you have two sets side by side, there are only two natural questions. Is it in this one OR that one? Is it in this one AND that one?
Presenter notes: Open with a live count. Ask everyone who plays football to stand, count them and write the number up. Sit them down, ask everyone who plays volleyball to stand, count and write that up. Add the two numbers out loud and ask whether that is how many people play at least one sport. Somebody will object that a few people stood up twice. That objection is the entire lesson, and it has arrived before you have written a single symbol.