In a 100 m race A beats B by 20 m, and in a 100 m race B beats C by 25 m. By how many metres does A beat C in a 100 m race?

Explanation

1. 01

   When A runs 100 m, B runs $80$ m.

2. 02

   C runs $\frac{75}{100}$ of what B runs: $80 \times \frac{75}{100} = 60$ m, so A wins by $40$ m.