Claim and explain [Meas 2.3/2]

An activity for a small group of children. Its purpose is to give practice in using the method with understanding.

Materials

• A set of cards with rectangles of various sizes all marked in centimetre squares. These are in pairs of equal area, e.g., 4 cm by 4 cm and 8 cm by 2 cm.*

* A suitable set is provided in the photomasters.

What they do

1. The pack is shuffled and put face down on the table. The top card is turned over and put centrally.
2. In turn, the players turn over the top card of the pile and put it centrally. If they see a pair of the same area, they claim it and explain how they know that the area is the same. ("Eight rows, two in each, sixteen square centimetres" is a better explanation than, say, "Eight twos are sixteen.") If they cannot see a pair, they say "No claim."
3. The player whose turn it is may begin by claiming any pair which has been overlooked. He then still has his turn as in step 2.
4. In the event that there is no face-up card when it comes to a player's turn, he may turn over two cards.
5. When all the cards have been turned over, the winner is the player with most pairs.

Sample "Claim and explain" cards

© Richard R. Skemp, 1994. SAIL through Mathematics, Volume 2.