Answer:
Its trying to trick you, you dont need any fancy shmancy formula. If you see the 8 its trying to make you think of a formula but if there is a formula and you get it wrong then you get it wrong. Its easy the 8 is there but a circle has a radius no matter where you measure it. 8/2 = 4. Radius is 4 Diameter is 8
Think outside the box
4 is radius 8 is diamater
