(a) ∵ Area of a triangle = √s(s−a)(s−b)(s−c)
Here, a = 13, b = 20 and c = 21 ∴ s =
13+20+21
2
=
54
2
= 27 ∴ Area of a triangle = √27(27−13)(27−20)(27−21) = √27×14×7×6 = √3×3×3×7×2×7×2×3 = 9 × 2 × 7 = 126m2 So, area of both triangles = 2 x 126 = 252 m2 Now area of sides = 30 x 13 + 30 x 20 = 390 + 600 = 990 m2 and area of rectangle = 30 x 21 = 630 m2 ∴ Total surface area of triangular prism = 252 + 990 + 630 = 1872 m2