I need help on this equation! pls help!

Acircular city park has a sidewalk directly through the middle that is 111 - feet long. if each bag of fertilizer covers 50 square feet, then determine how many bags of fertilizers the parks and recreation department needs to use to cover the circular park. ignore all the sidewalks around and through the park.

Just tell me how to set up the equation.

Write and solve a real word problem that involves determining distance on a coordinate plane