Serena and Venus Williams start 150m apart and begin running towards each other. Serena has a speed of 7.5 m/s and Venus has a speed of 5.0 m/s. How long does it take for them to meet?

- - Serena is running toward Venus at 7.5 m/s.

- - Venus is running toward Serena at 5.0 m/s.

- - The space between them is shrinking at (7.5 + 5.0) = 12.5 m/s.

- - The space started out at 150m wide.

It will shrink to zero after

(150 m) / (12.5 m/s) = 12 seconds