The chemistry teacher decides to use chalk paint to cover a circular portion of a wall in the science lab. If the greatest distance across the circle is is 3 feet, approximately how many square feet will the chalk paint cover?

Really need on these. i have no idea what to do

Amuffin recipe, which yields 12 muffins, calls for cup of milk for every 1 cups of flour. the same recipe calls for cup of coconut for every cup of chopped apple. to yield a batch of 30 muffins, how much flour will be needed in the mix?

If y varies directly as x2 and y=6 when x=6, find the constant of variation.