Calculate the diameter of a circle with area 80cm^2 to two significant figures.

First you need to remember the equation area of a circle = πr² with r being the radius. Therefore as we are given the area of the cicle we need to rearrange the equation to give us the radius. Therefore this gives us √(A/π) = r. Putting the numbers in using your calculator it gives us ≈ 5.046. However we need the diameter so this value needs to be multiplied by 2. Which gives us ≈ 10.09, but the question asks for only two significant figures therefore the correct aswer is 10.