Year 6 · Ratio and Proportion · Summary

Year 6 Ratio and Proportion: summary and key words

Part of the Year 6 ratio and proportion chapter. Chapter overview · whole chapter on one page

Chapter summary

Skill	Method
Ratio notation	a:b, read ‘a to b’. The order matters. Keep the amounts in the order the question gives.
Simplest form	Divide both numbers by their highest common factor (HCF).
Equivalent ratios	Multiply (or divide) both numbers by the same number.
Missing values	Find the scale: divide the given amount by the number it matches. Multiply the other number by the scale.
Similar shapes	Scale factor = new length ÷ old length. Multiply every old length by the scale factor.
Unequal sharing	Add the parts. Divide the total by the number of parts. Multiply each part by the value of one part.
Grouping	Find the amount in one group, then multiply by the number of groups. The total must be a multiple of the group size.

I can write a ratio in the right order and simplify it by dividing by the HCF.
I can find an equivalent ratio, and find a missing number by finding the scale.
I can find a scale factor and use it to find new lengths in similar shapes.
I can share an amount in a ratio, using the number of parts.
I can find the total from one share, and use fractions of a total.
I can work out totals for groups, such as packs and bags, that have a ratio in them.

Ratio: A comparison of two or more amounts of the same kind, written with a colon, such as 2:3.
Equivalent ratio: A ratio that describes the same mix, such as 2:3 and 4:6.
Scale factor: The number that every length in a shape is multiplied by to make a similar shape.
Similar shapes: Shapes with the same angles and with matching sides in the same ratio.
Part: One of the equal pieces in a ratio. Every part has the same size.
Highest common factor (HCF): The biggest number that divides exactly into two or more numbers.