Answer
$33,750\ units$
Work Step by Step
Step 1. As the power a windmill $p$ varies directly as the cube of the wind velocity $v$, we have $p=kv^3$ where $k$ is a constant.
Step 2. As $p=10,000$ when $v=10\ km/hr$, we have $10,000=k(10)^3$, thus $k=10$
Step 3. For $v=15\ km/hr$, we have $p=10(15)^3=33,750\ units$
