A quarter of the whole pie chart represents 20 people. A quarter is one of four equal parts, so if you multiply a quarter of the pie chart by 4, you can find out what the whole is. So: In this ...

Narrator: Pie charts are brilliant at showing proportions, comparing the parts of something ... then simplify again by dividing by 9; 3 over 8. So we know that 18 people are three eighths of ...