The cross section section of a uniform prism is... - WAEC Mathematics 2011 Question

A prism has 3 rectangular faces and 2 triangular faces and 2 rectangular faces = 10(3 + 4 + 5) = 120

Area of triangular faces = (\sqrt{s(s - a) (s - b) (s - c)})

where s = (\frac{a + b + c}{2})

= (\frac{3 + 4 + 5}{2})

= (\frac{12}{2})

= 6

Area of (\bigtriangleup) = (\sqrt{6(6 - 30(6 - 4)(6 - 5)})

= (\sqrt{6 \times 3 \times 2 \times 1}) = 6

Area of triangle faces = 2 x 6 = 12cm²

Total surface area = Area of rectangular face + Area of (\bigtriangleup) = 120 + 12

= 132cm²