The circumference of a circle is given by C = 2\(\pi\)r. Your question asks you to use 3.14 for pi. Radius is half of diameter, so halve those to fit it into the equation.
16). C = 23.147 = 44.0
17) C = 23.149 = 56.5
18) C = 22.1412 = 51.4
19) C = 22.146.4 = 27.4
