Question:
If a girl 5 feet tall could walk around the equator, how many feet further would the top of her head travel than her feet? Assume that the earth is a sphere. Express your answer in terms of $\pi$.

Answer:
Let $r$ be the radius of the earth in feet. The girl's feet travel along a circle of radius $r$, while the girl's head travels along a circle of radius $r+5$. The circumference of the first circle is $2\pi r$, while the circumference of the second circle is $2\pi(r+5) = 2\pi r + 10\pi$. So her head travels $(2\pi r + 10\pi) - 2\pi r = \boxed{10\pi}$ feet more than her feet.