Cannonballs are stacked in a pyramid shape with a triangular base of 5 cannonballs on a side. how many cannonballs in all are in the stack?

Simply add 5,4,3,2, and 1 together to get 15. each row gets smaller by 1, so simply keep adding until you get to 0.

Ithink its 126 hope its

You have 2 sides that are 2 cms and you have 6 sides that are 1/2 cm and you have 4 sides that are 1 cm. the smallest sides are 1/2 the medium sized sides are 1 and the smallest are 1/2. so to find the perimeter you have to add them all up together so your answer will be 11 cm's