Donna makes a round pizza she wants to put a cheese layer on the pizza. If the cake is 8 cm in diameter, how many square cm of cheese layer dose she need to put on the pizza?

To solve this problem you would use the area. The formula is A=pi x radius^2. So radius is half of diameter and the diameter is 8 so r=4. So everything comes to 16pi. This is if the question says to leave your answer in terms of Pi. If it doesn't say anything it would be acceptable to leave your answer this way. But you can also use 3.14 as an approximation for Pi.