Answer:
126sq cm
Explanation:
Let s be the semi-perimeter of the triangular base of the prism. Then,
S = (13 + 20 + 21)/2 cm. = 27 cm.
Therefore, the area of the prism = √[s(s - a)(s - b)(s - c)]
= √(27(27 - 13)(27 - 20)(27 - 21)) sq. cm.
= √(27 × 14 × 7 × 6) sq. cm.
= 9 × 7 × 2 sq. cm.
= 63 *2
=126sq cm
Hope this helps!!!