Answer :
abh/6
a=apothem length
b=side length of the base
h=height
if we factor the formula for area of a triangular pryamid, we get (1/2ab)(h/3)
1/2ab= area of the triangular base
so 12.6(5/3)=21
a=apothem length
b=side length of the base
h=height
if we factor the formula for area of a triangular pryamid, we get (1/2ab)(h/3)
1/2ab= area of the triangular base
so 12.6(5/3)=21