The formula for the area of a circle is A=πr^2. The radius, (r) is half of the diameter. The diameter of this circle is 10 in, so the radius is 5 in. Plug 5 into the formula A=πr^2 to get A=π5^2. Square 5 to get 25 and plug it back in the formula to have A=25π. Multiply pi (π, 3.14) by 25 to get 78.5.
When the amount found when Bob measured [5.12] is divided by the actual [6] the result is .853333, which is the percentage that Bob measured as compared to the actual. amount of error is 15% (100%-85%)
