A runs 400 m in 80 seconds and B runs it in 100 seconds. How much of a start, in metres, should A give B for a dead heat in a 400 m race?

Explanation

1. 01

   B's speed is $\frac{400}{100} = 4$ m/s. In A's 80 seconds, B runs $4 \times 80 = 320$ m.

2. 02

   So B needs a start of $400 - 320 = 80$ m.