Sort with One Clear Rule

Supplied materials

• Paper and pencil; an adult may read aloud. No device, account or purchase is needed.

Learn the idea

Sorting instructions tell us what to look for. This paper rule says put every triangle in box T and every other shape in box O. We check the shape of each card. A color might be interesting, but this rule does not ask about color, so it cannot change the box.

Draw four cards: a red triangle, a blue circle, a blue triangle and a red square. Make two drawn boxes T and O. Process one card at a time and say triangle or other before placing it. Each card goes in exactly one box; the word every includes both triangles.

1. Draw the four supplied cards and the two boxes.
2. Read the rule aloud and point to the property it uses: shape.
3. Place the cards one at a time, keeping the red and blue triangles together in T.
4. Count each box and check that all four cards appear once.

Check your reasoning

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Take it further

Change the rule to put every blue card in B and every other card in O. With the original four cards, B contains the blue circle and blue triangle; O contains the red triangle and red square. Both counts remain 2.

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