Question

Find the area of $△$ two sides are $18cm$, $10cm$ if perimeter is $42cm$

Answer 1

Let the third side be $xcm$

$\therefore 42=18+10+x$

$\therefore x=42-28=14cm$

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

Here $s=\frac{42}{2}=21cm$

$a=18cm,b=10cm,c=14cm$

$\therefore$ Area = $\sqrt{21(21-18)(21-10)(21-14)}$

$\therefore$ Area = $\sqrt{21\times 3\times 11\times 7}$

$\therefore$ Area = $\sqrt{21\times 21\times 11}$

$\therefore$ Area = $21\sqrt{11}c{m}^2$

Hence area is $21\sqrt{11}c{m}^2$