Efficient Subtraction Year 4 Addition and Subtraction Learning Video Clip

Step 8: Efficient Subtraction Year 4 Addition and Subtraction Learning Video Clip

Sebastian the explorer has left his camp and wandered into an unexplored part of the jungle. He finds himself in danger and needs to use his knowledge of efficient subtraction to get back to safety.

More resources for Autumn Block 2 Step 8.

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Discussion points for teachers

1. How many more steps must he make?
Discuss efficient subtraction and the different methods that can be used. Discuss which is most appropriate for this question.
7,991 – 4,958 = 3,033

2. Which three calculations can be done by counting on? Complete the calculations.
Discuss what counting on involves. Discuss when this works well and the types of questions it is not appropriate for.
2,107 – 2,096 = 11; 3,749 – 3,698 = 51; 1,026 – 989 = 37

3. Create a subtraction that can be calculated efficiently that provides this answer so that Sebastian can travel down the vines.
Discuss the different combinations that can be made to create the answer. Discuss what method is the most efficient for the subtraction, is there more than one method that is efficient? This question is open-ended for the children to explore.
Various answers, for example: 4,537 – 3,000 = 1,537  

4. How much does he have left? Discuss what is involved in this question as it is has more than one step.
Discuss the most efficient method to use to solve this calculation.
291 + 119 = 410ml; 1,000 – 410 = 590ml

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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