Question

Earth circumference is approximately 25,000 miles. If you could dig a tunnel to the center of the earth, how long will the tunnel be?

Answer 1

Check the picture below.

`\textit{Circumference of a Circle}\\\\ C=2\pi r ~~ \begin{cases} r=radius\\[-0.5em] \hrulefill\\ C=25000 \end{cases}\implies 25000=2\pi r \\\\\\ \cfrac{25000}{2\pi }=r\implies \stackrel{ miles }{3978.87}\approx r`