



 
Hi Cynthia. The formula for the area of a circle is one you should try to memorize:
where A is the area and r is the radius. Sometimes you don't know the radius, but you do know the diameter. You should also know that 2r = d, where d is the diameter. That means the radius is half the diameter. If you have a circular garden that is 20 feet in diameter, then its radius is 10 feet. That means r = 10, so
Hope this helps,  


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