In a 1 km race the speeds of A and B are in the ratio 5 : 4, and A gives B a start of 150 m. By how many metres does A win?

Explanation

1. 01

   When A runs 1,000 m, B runs $1{,}000 \times \frac{4}{5} = 800$ m.

2. 02

   B had 850 m to run, so A finishes with B still 50 m short.