i thort i was ok at maths but apparently not (graphic design student)

is this fairly complicated or butt easy? i am making a sphere out of 15degree cones. the cones vary in length but i wouldnt have thort this mattered? if all the cones are joined from the center, how many should i need to complete an entire sphere? obv it would take 24 to cover the basic 'diameter' (sorry if i'm not being very accurate with terminology) but then how do i calculate the rest?

need an answer asap because it affects how much materials i pay for etc
thanks