Mathematics

Adding and subtracting fractions

In this unit, students will review the properties of fractions and the concept of equivalence in order to competently add and subtract fractions with both like and unlike denominators. They will also calculate with and convert between improper fractions and mixed numbers. Placing fraction problems in context is important in order to further develop conceptual understanding. Students will be asked to notice how operations involving fractions are different to those of whole numbers.

Key questions

• How are equivalent fractions helpful when adding and subtracting fractions?

• Which strategies are helpful when solving problems involving addition or subtraction of fractions?

• What models can we use to help us add and subtract fractions with different denominators?

Students will use pattern blocks to represent fractions.

Fractions feature in the real world outside the classroom too. Solving problems with fractions in them features heavily in this unit. Fractions allow us to solve problems that are not possible to solve with just whole numbers. For example:

40 students tried out for the kite flying team. 5/8 of the students were boys. How many girls tried out? Draw a picture and solve it.

This one requires students to understand denominators and needs more steps to solve:

Chris and Mike are training for a race. Chris ran 2 ¾ km and Mike ran 3 ⅝ km. How many km did they run in total?

Next unit: Multiplying fractions