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OUTCOME
A student:
MA1-5NA: uses a range of strategies and informal recording methods for addition and subtraction involving one- and two-digit numbers
Teaching Point | Some students may need assistance when two tenses are used within the one problem, eg ‘I had six beans and took away four. So, how many do I have now?’ |
The word ‘left’ can be confusing for students, eg ‘There were five children in the room. Three went to lunch. How many are left?’ Is the question asking how many children are remaining in the room, or how many children went to lunch? |
| Language | Students should be able to communicate using the following language: plus, add, take away, minus, the difference between, equals, is equal to, empty number line, strategy. |
Strategies | Jump strategy on a number line – an addition or subtraction strategy in which the student places the first number on an empty number line and then counts forward or backwards, first by tens and then by ones, to perform a calculation. (The number of jumps will reduce with increased understanding.) Jump strategy method: eg 46 + 33
Two number lines show different ways of adding numbers using small and large increments. Jump strategy method: eg 79 – 33
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Split strategy – an addition or subtraction strategy in which the student separates the tens from the units and adds or subtracts each separately before combining to obtain the final answer. Split strategy method: eg 46 + 33 46+33 | |
Inverse strategy – a subtraction strategy in which the student adds forward from the smaller number to obtain the larger number, and so obtains the answer to the subtraction calculation. Inverse strategy method: eg 65 – 37 start at 37 An inverse operation is an operation that reverses the effect of the original operation. Addition and subtraction are inverse operations; multiplication and division are inverse operations. |
Explore the connection between addition and subtraction | use concrete materials to model how addition and subtraction are inverse operations |
| use related addition and subtraction number facts to at least 20, eg 15 + 3 = 18, so 18 – 3 = 15 and 18 – 15 = 3 |
Solve simple addition and subtraction problems using a range of efficient mental and written strategies | use and record a range of mental strategies to solve addition and subtraction problems involving two-digit numbers, including: |
| the jump strategy on an empty number line | |
| the split strategy, eg record how the answer to 37 + 45 was obtained using the split strategy 30+40=70 7+5=12 so 70+12=82 | |
| an inverse strategy to change a subtraction into an addition, eg 54 – 38: start at 38, adding 2 makes 40, then adding 10 makes 50, then adding 4 makes 54, and so the answer is 2 + 10 + 4 = 16 | |
| select and use a variety of strategies to solve addition and subtraction problems involving one- and two-digit numbers | |
| perform simple calculations with money, eg buying items from a class shop and giving change (Problem Solving) | |
| check solutions using a different strategy (Problem Solving) | |
| recognise which strategies are more efficient and explain why (Communicating, Reasoning) | |
| explain or demonstrate how an answer was obtained for addition and subtraction problems, eg show how the answer to 15 + 8 was obtained using a jump strategy on an empty number line (Communicating, Reasoning)  |
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