A ratio compares two or more amounts of the same kind, written with a colon like 2 : 3. The order matters — 2 : 3 is not the same as 3 : 2. For example, if a class has 2 boys for every 3 girls, the ratio of boys to girls is 2 : 3, while girls to boys is 3 : 2. Always read carefully which amount is named first.
Worked example
Problem A class has 8 boys and 12 girls. Write the ratio of boys to girls in its simplest form.
Write the two amounts in the order asked: boys : girls = 8 : 12.
Find the highest common factor of 8 and 12 — it is 4.
Divide each part by 4: 8 ÷ 4 : 12 ÷ 4 = 2 : 3.
Watch out Order matters — girls : boys would be 3 : 2.