What is a ratio?
A ratio compares two amounts. We write it with a colon, like 2 : 3. The ratio 2 : 3 means "for every 2 of the first thing, there are 3 of the second".
Key idea
To simplify a ratio, divide both numbers by the same number (their common factor), just like a fraction. Keep going until they cannot be divided by the same number again.
Simplifying
A ratio in its simplest form uses the smallest whole numbers. To add up parts, count all the numbers in the ratio.
Worked example
There are 4 red apples and 6 green apples. Ratio red : green = 4 : 6.
Divide both by 2: 4 ÷ 2 = 2 and 6 ÷ 2 = 3.
Simplest form = 2 : 3. Total parts = 2 + 3 = 5.
Remember
- Divide both sides by the same number to simplify.
- Keep the order the same as the question.
- Total parts = add all numbers in the ratio.