Question

Find the area of triangle whose sides are 9cm ,12cm nd 15cm

Answer 1

Let the sides be a, b and c.

a = 9 cm, b = 12cm, c = 15 cm.

Perimeter (P) = 9 + 12 + 15 = 36 cm.

∴ Semi-Perimeter (S) = P÷2

                                   = 18cm.

By Heron's formula,

A = √s(s-a) (s-b) (s-c)

   = √18 (18 - 9) (18-12) (18-15)

   = √18 (9) (6) (3)

   = √18 × 9 × 18

   = 3 × 18 = 54

∴Area of the triangle = 54 cm².