# Use knowledge of calculating within 20 to solve problems

I can use knowledge of subtraction to solve problems in a range of contexts.

# Use knowledge of calculating within 20 to solve problems

I can use knowledge of subtraction to solve problems in a range of contexts.

## Lesson details

### Key learning points

- When adding three addends, it is efficient to first add two addends using a known fact e.g. pair to 10 or double.
- When adding, we can bridge 10 by partitioning a part so that we can ‘make 10’.
- When subtracting, we can bridge 10 by partitioning a part to create a part that is equal to the ones digit of whole.
- The difference can be found through subtraction.

### Common misconception

Without correct representation, children may struggle to know what to calculate.

If needed, provide support at this stage so that the structure of the mathematics is clear to children.

### Keywords

Visualise - To imagine a given problem before us in real life.

Represent - To communicate mathematical ideas through models.

Calculate - To choose one of the four operations to solve a problem.

Efficient - Not wasting time or effort. An efficient strategy is one we can carry out easily.

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Video

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