Step 10: Checking Strategies Year 4 Addition and Subtraction Learning Video Clip
Sebastian the explorer is getting ready to leave the jungle and return home. Before he goes, he needs to make sure that all the data he has collected during his trip is accurate by using his knowledge of checking strategies.
More resources for Autumn Block 2 Step 10.
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Discussion points for teachers
- Help Sebastian use the inverse method for each calculation to check they are correct. Discuss what the inverse is. Discuss the order of numbers when using the inverse.
8,085 – 2,804 = 5,281; 647 + 812 = 1,459; 2,138 + 3,426 = 5,609;
3,348 – 2,549 = 799
- If any are incorrect, what should they be? Discuss what has gone wrong in the calculations. Discuss what the correct answers should be.
1,458 – 812 = 646; 2,549 + 789 = 3,338
- What could the possible missing values be? Discuss the different combinations that can be made to create the answer. Discuss the most efficient way to do this. Discuss how to ensure numbers are not repeated. This question is open-ended for the children to explore.
Various answers, for example:
- Help Sebastian to work out what the missing numbers should be. Discuss which digits are already known. Discuss how to use the inverse to identify the missing digits. Discuss the order of numbers when using the inverse.
5,883 + 3,742 = 9,625; 9,625 – 5,883 = 3,742; 4,019 + 2,573 = 6,592; 6,592 – 2,573 = 4,019
- Help him work out which operation will be the most efficient to check these figures. Discuss what the possible operations to use are. Discuss counting up and adding on to make calculating quicker.
5,621 + 2,236 = 7,857; 9,321 – 4,321 = 5,000; Change to 1,120 + 6,883 = 8,003; 3,758 + 2,265 = 6,023
National Curriculum Objectives
Mathematics Year 4: (4C2) Add and subtract numbers with up to 4 digits using the formal written methods of columnar addition and subtraction where appropriate
Mathematics Year 4: (4C3) Estimate and use inverse operations to check answers to a calculation
Mathematics Year 4: (4C4) Solve addition and subtraction two-step problems in contexts, deciding which operations and methods to use and why
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