Here is a hoop labelled has four sides and a second hoop labelled is red. Where would a red triangle go? And where would a red square go?

Watch the board with me. You might be asked to say a region out loud, so keep your eyes on where each card lands.

First a single hoop for one rule: test the rule, and the card is either in or out.

Now two circles that cross. The little space where the two circles cross is called the overlap. A card only goes in the overlap when both rules are true for it.

This last one has two rules again. Watch for a card that follows neither rule — where do you think it goes?

Our two rules today are has straight sides and is shaded.

We sort these five cards together: a shaded square, a plain circle, a shaded hexagon, a plain triangle, and a shaded circle. For each card we test both rules, then decide if it goes in one circle, in the overlap, or outside both.

We work through four sorts together on the board, each one harder than the last:

• Numbers by one rule: odd or even.
• Numbers by two rules, so some numbers land in the overlap.
• Shapes with a tricky card for the overlap.
• A mixed set with one card that sits outside both circles.