In a 400 m race, A beats B by 40 m or by 8 seconds. How long does A take to run the race?

Explanation

1. 01

   B runs the last 40 m in 8 seconds, so B's speed is 5 m/s and B takes $\frac{400}{5} = 80$ seconds.

2. 02

   A finishes 8 seconds earlier: 72 seconds.