Answer:
Option D. 18 in
Step-by-step explanation:
Since volume of a rectangular pyramid has a volume = 1512 in³
Height of pyramid = 12 in
Rectangular base having length = 21 in
we have to find the width of the base of pyramid.
Since volume of pyramid =
1512 = 4(21b)
1512 = 84b
Therefore width of the rectangular base of pyramid is 18 in
Option D is the answer.