Question

The edges of a triangular board are 6 cm, 8 cm and 10 cm. The cost of painting it at the rate of 25 paise per $c{m}^2$ is Rs. ___

Answer 1

$a=6cm,b=8cm,c=10\text{cm}$
$s=\frac{a+b+c}{2}$
$s=\frac{6+8+10}{2}$
$=12cm$
$A=\sqrt{s(s-a)(s-b)(s-c)}$
$A=\sqrt{12(12-6)(12-8)(12-10)}$
$=24{\text{cm}}^2$
The cost of painting it $=24\times 25=600$ paise
$=\text{Rs.}6$