Are you so sure
↓
These are just some
equivalent fractions of 1/2:
1/2 = 2/4 = 3/6 = 4/8
= 5/10 = 6/12 = 7/14 = 8/16
= 9/18 = 10/20 = 11/22 = 12/24
= 13/26 = 14/28 = 15/30 = 16/32
= 17/34 = 18/36 = 19/38 = 20/40
= 21/42 = 22/44 = 23/46 = 24/48
= 25/50 = 26/52 = 27/54 = 28/56
= 29/58 = 30/60 = 31/62 = 32/64
= 33/66 = 34/68 = 35/70 = 36/72
= 37/74 = 38/76 = 39/78 = 40/80
= 41/82 = 42/84 = 43/86 = 44/88
= 45/90 = 46/92 = 47/94 = 48/96
= 49/98 = 50/100 = 51/102 = 52/104
= 53/106 = 54/108 = 55/110 = 56/112
= 57/114 = 58/116 = 59/118 = 60/120
= 61/122 = 62/124 = 63/126 = 64/128
= 65/130 = 66/132 = 67/134 = 68/136
= 69/138 = 70/140 = 71/142 = 72/144
= 73/146 = 74/148 = 75/150 = 76/152
= 77/154 = 78/156 = 79/158 = 80/160
= 81/162 = 82/164 = 83/166 = 84/168
= 85/170 = 86/172 = 87/174 = 88/176
= 89/178 = 90/180 = 91/182 = 92/184
= 93/186 = 94/188 = 95/190 = 96/192
= 97/194 = 98/196 = 99/198 = 100/200
so if the diameter is 16, radius (r) = 8