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Students learn how to use ratio notation to solve problems ranging from interpreting the scale of a map to calculating a speed, distance or time.

This unit takes place in Term 3 of Year 8 and follows on from multiplying and dividing with fractions.

- Work interchangeably with terminating decimals and their corresponding fractions.
- Define percentage as ‘number of parts per hundred’, interpret percentages and percentage changes as a fraction or a decimal
- Interpret fractions and percentages as operators

- If the ratio between two things is the same they are in direct proportion.
- To divide an amount in a given ratio find the value of one share by finding the total number of shares, then divide the amount by the total number of shares.
- To compare values work out the cost per unit or number of units per pound or penny. This takes the form of 1 : n.
- A common misconception is to write the ratio of 2 : 3 as 2/3. Emphasise the need to consider the total number of shares when writing a ratio as an equivalent fraction or percentage.

Develop fluency

- Consolidate their numerical and mathematical capability from key stage 2 and extend

their understanding of the number system - Select and use appropriate calculation strategies to solve increasingly complex problems

Reason mathematically

- Extend their understanding of the number system; make connections between number

relationships, and their algebraic and graphical representations - Extend and formalise their knowledge of ratio and proportion in working with measures

and geometry, and in formulating proportional relations algebraically

Solve problems

- Develop their mathematical knowledge, in part through solving problems and evaluating

the outcomes, including multi-step problems - Select appropriate concepts, methods and techniques to apply to unfamiliar and non-routine problems.

Ratio, proportion and rates of change

- Change freely between related standard units [for example time, length, area, volume/capacity, mass]
- Use scale factors, scale diagrams and maps
- Express one quantity as a fraction of another, where the fraction is less than 1 and greater than 1
- Use ratio notation, including reduction to simplest form
- Divide a given quantity into two parts in a given part:part or part:whole ratio; express the division of a quantity into two parts as a ratio
- Understand that a multiplicative relationship between two quantities can be expressed as a ratio or a fraction
- Relate the language of ratios and the associated calculations to the arithmetic of fractions
- Solve problems involving direct and inverse proportion, including graphical and algebraic representations
- Use compound units such as speed, unit pricing and density to solve problems.

March 10, 2019

When calculating the volume of a pyramid we can substitute the values of the length, width and perpendicular height into the formula V = 1/3 lwh. In my experience this is often provided for the students with little explanation as to why a volume of a pyramid is exactly one third the volume of a […]

March 4, 2019

When teaching solving 3D problems using trigonometry we begin the lesson with a recap of Pythagoras’ Theorem and the three trigonometric ratios. We do this by matching the ratio and equations to the respective right-angled triangle. Students are encouraged to work in pairs and to show the diagrams as part of the working out on […]

January 29, 2019

When I teach rounding to a significant figure, I ask the class to discuss in pairs or small groups a definition for the word significant. It is a word that all the students have heard before but not all are able to define. After 2 or 3 minutes of conversation I ask the students to […]