Combining ratios | Maths | Quizalize & Oak National Academy

Starter quiz

LCM is an abbreviation for lowest common ______.

'multiple' ✓
What is the ratio of hearts : smileys?

'5 : 3' ✓
What is the HCF of 24 and 18?

'6' ✓
What is the ratio of hearts : smileys? (Give your answer in its simplest form)

'3 : 4' ✓
What is the LCM of 4 and 6?

'12' ✓
Match each ratio to an equivalent ratio.

4 : 3

⇔

16 : 12 ✓

7 : 6

⇔

14 : 12 ✓

2 : 5

⇔

16 : 40 ✓

3 : 8

⇔

12 : 32 ✓

6 : 11

⇔

12 : 22 ✓

What is LCM an abbreviation for?

'lowest common multiple' ✓
Given these bar models, what is the ratio of hearts to suns?

'5 : 2' ✓
Given that squares : circles = 4 : 3 and circles : triangles = 1 : 5, find the ratio of squares : triangles.

'4 : 15' ✓
a : b = 2 : 5, b : c = 6 : 7. Find the ratio a : b : c

'12 : 30 : 35' ✓
A box contains 212 sweets which are either hearts (h), stars (s) or bottles (b). The ratio of hearts to stars is 5 : 3. The ratio of stars to bottles is 4 : 7. How many stars are in the box?

'48' ✓
b = 4a, c = 5b, find the ratio of a : c

'1 : 20' ✓

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There may be a relationship between quantities A and B and a relationship between quantities B and C
Therefore there is a relationship between A and C
If A : B and B : C then A : B : C and A : C
When the common quantity is not the same in each ratio, equivalent ratios can be used
For example, if A:B and 2B:5C then 2A:2B:5C and 2A:5C

Combining ratios without using equivalent ratios to equate the common part.

Pupils may need to spend extra time finding equivalent ratios and looking at when it is ok to combine ratios or not.

Proportion - A part to whole (sometimes part to part) comparison. If two things are proportional then the ratio of part to whole is maintained and the multiplicative relationship between parts is also maintained.
Ratio - A ratio shows the relative sizes of 2 or more values and allows you to compare a part with another part in a whole.
Lcm - LCM is an abbreviation for lowest common multiple.
Lowest common multiple - The lowest common multiple is the lowest number that is a multiple of two or more numbers.