Find the area of a triangle whose sides are 12 cm, 9.6 cm and 7.2 cm.

Consider a = 12 cm, b = 9.6 cm and c = 7.2 cm

We know that,

Semi perimeter (s) = $\dfrac{(a + b + c)}{2}$

Substituting the values we get,

s = $\dfrac{(12 + 9.6 + 7.2)}{2} = \dfrac{28.8}{2}$ = 14.4 cm.

Area of triangle = $\sqrt{s(s - a)(s - b)(s - c)}$

Substituting values we get,

$A = \sqrt{14.4(14.4 - 12)(14.4 - 9.6)(14.4 - 7.2)} \\[1em] = \sqrt{14.4 \times 2.4 \times 4.8 \times 7.2} \\[1em] = \sqrt{1194.39} \\[1em] = 34.56 \space \text{cm}^2.$

Hence, area of triangle = 34.56 cm².