circumference = Pi * d = Pi * 2 * r
area = Pi * (d/2)^2 = Pi * r^2
16)
circumference = 3.14 * 2 * 7 = 43.96
area = 3.14 * 7^2 = 153.86
17)
circumference = 3.14 * 18 = 56.52
area = 3.14 * (18/2)^2 = 254.34
18)
circumference = 3.14 * 24 = 75.36
area = 3.14 * (24/2)^2 = 452.16
19)
circumference = 2 * 3.14 * 6.4 = 40.192
area = 3.14 * 6.4^2 = 128.6144