to work out surface area you have to;
to work out the volume of a cone;
1) work out the area of the base of a cone. by; find the radius or half the diameter and use the formula πr³ (pi X radius cubed) divided by 3 then multiplied by 4.
2) then multiply the area by the height of the cone ( the height of the cone from base to the point, not length of the cone on the outside)
3) now divide your total by 3... now you have your answer