In a 100 m race, A beats B by 10 m, and in another 100 m race B beats C by 10 m. By how many metres would A beat C in a 100 m race?

Explanation

1. 01

   When A runs 100 m, B runs 90 m. When B runs 90 m, C runs $\frac{90}{100} \times 90 = 81$ m.

2. 02

   So A beats C by $100 - 81 = 19$ m.