Rich tasks
- This is an open-ended activity that requires students to create and then solve two-digit addition and subtraction problems. The task can be given at any point during the chapter. The first part of the task could be done in class or for homework, while the comparison and discussion of strategies will need to be completed in class.
- It's dicey
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1. It's dicey
- This activity provides a valuable opportunity for every student to explain to a partner the strategy they have used. It is a good idea to suggest students record their strategy in some way, or practise their explanations (with materials perhaps) in case they are asked to share the strategy later. This activity provides a valuable opportunity for every student to explain and justify the strategy they think most efficiently solves each problem. Encourage students to question their peers if they don’t understand or need clarification about a strategy and to give reasons why one strategy might be quicker or easier than another.
- Partner conversations are a very important aspect of the task and roaming the class as students talk with their partners gives teachers an opportunity to hear this discussion, and perhaps the chance to find students with problems or strategies it might be valuable to share with the whole class.
Adding by choosing a strategy page 100
- Solve addition problems using a variety of strategies.
- Explore ways of recording each strategy, including empty number lines and equations.
- Justify why a particular addition strategy is more efficient than others.
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Teacher notes
- Students frequently use a ‘safe’ strategy rather than practising a range of strategies and discovering which are most efficient. It is important that students are encouraged to move out of their comfort zone and try different strategies.
- Models, such as those on page 100 of the student book, provide a scaffold that students can refer to when working through
Activity 1. - Making a wall display or including a page with ’models’ in their workbooks can help students working independently or with a partner to decide which strategy might be best. These are most effective if students create them for themselves. If students are given examples to practise at home, it is also helpful for parents to have a copy so they can be aware of strategies their child is familiar with.
- Students may not all choose the same strategy as being quicker or more efficient. Often this is just a matter of personal preference, but in some instances, it may also indicate that students are struggling to recall basic facts or have not consolidated their place value understanding and consequently are avoiding some strategies that might prove helpful. Identifying and providing extra opportunity for practice or specific instruction on an area of uncertainty will promote more flexible use of strategies.
Subtracting by choosing a strategy page 102
- Solve subtraction problems using a range of strategies.
- Explore ways of recording each strategy, including empty number lines and equations.
- Justify why one subtraction strategy is more efficient than others..
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Teacher notes
- Subtraction can be used to solve problems that require taking a quantity away or finding the difference between two quantities. Both can be solved by subtracting in parts (e.g. splitting in a way that jumps through a tens number), or by place value.
Adding and subtracting by choosing a strategy page 104
- Solve addition and subtraction problems with an efficient strategy.
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Teacher notes
- Students will become more flexible and fluent in moving between addition and subtraction through these activities, games and puzzles. Encourage students to look back at the examples in the earlier sections if they are having difficulty.
- Encouraging students to work in groups gives them opportunity to share strategies and learn from each other as they practise and solve puzzles together.
