Adding and subtracting fractions: the same sized slice
Teacher’s Notes

These exercises and activities are for students to use independently of the teacher to practice number properties.

Number Framework domain and stage:

Fractions, ratios and proportions, stages 5 to 6, early additive to advanced additive

Curriculum reference:

Number, level 6

Numeracy Project book reference:

These activities can be used to follow the teaching episodes based on, Book 8, page 5, fractions in a whole and are for those students who are able to use the associated number properties.

Prior knowledge. Students should be able to:

During these activities, students will meet:

Background

Before this activity is commenced, students should have learnt that fractions can be smaller than one, can equal one, and be greater than one, and can relate drawings to numeric fractions. It is also useful if they can convert improper fractions to mixed numbers, though as the students are at stage 5 this is likely to be using additive methods rather than multiplicative ones.

Exercise 1
Exercise 1 is an exploration that hopes to build on students’ existing knowledge about fractions to help students establish/invent a strategy for adding simple fractions. The first problems have both a word story and a set of drawings to represent the story mathematically. Some students may need to be introduced to the idea that both of these representations show the same thing. The next problems rely simply on the drawings. Once students have developed a strategy for adding such fractions, they are then invited to use this on some numeric fractions

Exercise 2: Parts in a whole
This exercise is a simple exercise for students who need to revisit the idea that n/n = 1

Exercise 3

These problems involve addition of fractions with like denominators. Many have answers that are greater than one. Students who have learned to convert improper fractions to mixed numbers should be challenged to make this conversion, even though the answers do not provide this format. Likewise, answers are not simplified as students at this stage cannot be expected to understand multiplicative processes.

Investigation
This investigation challenges students to think about subtraction of fractions with like denominators, again starting with story problems and drawings that show these. Some students may find it challenging to make up the word problems required, or how this could be represented with drawings. This investigation can form part of a teaching session which covers the same concepts.

Exercise 4
Basic subtractions with like denominators

Practice exercises with answers:

PDF (77KB) or Word (32KB)