Finding unknown ratios

Using a table can help to answer problems when one or more ratios are incomplete or unknown.

Example

Some boys and girls are divided into teams in the ratio 3:4. There are 8 girls in one team. How many boys are there in the team?

There are 8 girls shared into 4 parts. Each part has \frac{8}{4} = 2 \:\text{girls}.

Fill in the table using this information.

Boys (3)Girls (4)
2222

Because each part is equal, the rest of the table can now be filled in.

Boys (3)Girls (4)
2222222

From the table it is clear that the number of boys in the team is 3 \times 2 = 6.