Question

A solid triangular prism with equilateral base is 5 centimetres high and its base perimeter is 12 centimetres. Find its surface area.

Answer 1

Height of the prism = 5 cm

Base perimeter = 12 cm

Lateral surface area of the prism = Base perimeter × Height of the prism

= 12 cm × 5 cm

= 60 cm²

Base of the prism is an equilateral triangle with perimeter 12 cm.

⇒ 3 × length of side = 12 cm

⇒ Length of each side = 4 cm

Area of the equilateral triangle =

∴ Surface area of the prism = Lateral surface area of the prism + 2 × Area of the equilateral triangle

= (60 + 2 × ) cm²

= (60 + 8 × 1.73) cm²

= 73.84 cm²