Answer:
A) 220.5 mm^2
Step-by-step explanation:
<u>Explanation</u>:-
Given A regular triangular pyramid has a base of area is 31.5mm^2
and also given surface area of triangular pyramid is 252 mm ^2
by using formula
surface area of regular triangular pyramid = base of area + half of lateral surface.
252 = 31.5 +
220.5 = lateral area of triangular pyramid
lateral area of triangular pyramid = 220.5 mm^2