Key learning points

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

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.

Common misconception