You can put this solution on YOUR website! CIRCUMFERANCE=2piR
28=2*3.14*R
28=6.28R
R=28/6.28
R=4.4586 THIS IS THE RADIUS.
SEEING AS THE DIAMETER IS TWICE THE RADIUS. WE MULTIPLY THE R BY 2 & WE GET
2*4.4586=8.9172 WHICH IS THE DIAMETER OF A CIRCLE WITH A CIRCUMFERANCE OF 28.