What is a radius in geometry, and what are some examples of it?

Janie has $3. she earns $1.20 for each chore she does and can do fractions of chores. she wants to earn enough money to buy a cd for $13.50. write an inequality to determine the number of chores, c, janie could do to have enough money to buy the cd.

An ant travels at a constant rate of 30cm every 2 minutes.at what speed does the ant travel per minute

The area of a circle is equal to 1 dm². find the radius of the circle.