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This displays a set of cards: five that are best done using a place value partitioning strategy, five that are best done using a tidy numbers strategy and five that could be done either way with almost the same efficiency.

Give the cards out. You may need two sets of cards so that everyone gets a card, or you could put the students into pairs.

Ask the students who think the calculation on their card is best done using place value to stand in one corner, the ones with cards best done using tidy numbers in another corner and the ones that could be either in a third corner.

Tell them there should be ten in each group. If they have more than ten, they need to decide which students have cards that do not fit. If they have fewer than ten, they need to find students with cards that do fit so they end up with exactly ten in their group.

The group must give a mathematical reason why a card doesn’t fit in a group.

You could now ask students to solve the problem on their card.

This displays four different word problems: one best solved by place value partitioning, one by using tidy numbers, one “how many more” best solved by place value and one “how many more” best solved by jumping up through a tidy number or adding on a tidy number.

Students are asked to solve each problem.

Discuss what strategies students used for each.

If different strategies were used, ask students who each used different ways to lobby that their way is best.

At the end take a vote from the class/group as to which way they think is most efficient.

This displays students discussing different strategies.