Mathematics

Problem

Under a

20

-ft streetlamp, a

5

-ft tall runner moves directly away from the lamp. At the moment the runner is

15\text{ ft}

from the base, the tip of the runner’s shadow is moving at

8\text{ ft/s}

. How fast is the runner moving at that instant? a)

8\text{ ft/s}

6\text{ ft/s}

12\text{ ft/s}

6.4\text{ ft/s}