Disco Balls
Disco Balls goes up in front of the whole class, and again, the kids don't get to know the rules. You just say, "You have to make 15. What are your ideas?" Maybe someone tries 5, 5 and 5, but that makes 125, so that isn't right. Then you go to Simon. You're pointing to individual kids, not having hands raised. Simon says 3, and then 5, and maybe he got lucky, but look: 3 times 5 is equal to 15. But it looks like we've got a second disco ball. Gertrude says 2 times 7. That's 14, so close. And then someone has the idea of 5 times 3, and that's the solution.
So what's this showing? Normally, 3 times 5 is the same as 5 times 3. But not here. Here, multiplication is not commutative: 3 times 5 produces a different disco ball than 5 times 3. You can only build with 2, 3, 5 and 7, because those are the prime numbers. So a child making 48 might think: 48 is even, so I'll start with a 2. It's a multiple of 8, and 8 times 6 is 48, but I don't see a 6. That's because 6 isn't a prime number. 6 is 2 times 3.
And then it turns out there's a whole bunch of solutions for 48: 2 times 2 times 2 times 2 times 3, then 2 times 2 times 2 times 3 times 2, moving the 3 around. Kids won't get these as fast as I do. They'll go at a much more relaxed pace, and they'll fail a lot, let's be honest. This is all about getting organized. Sometimes it's not enough to find one solution. We want to find all of the solutions.
- Grades
- 2–6
- Subjects
- Multiplying & Dividing
- Kind
- Puzzle
Eye of Horus
Diversity City
Fractured Fractions