Question

The area of a triangle whose sides are $13cm,14cm$ and $15cm$ is:

• A. $42c{m}^2$
• B. $86c{m}^2$
• C. $84c{m}^2$
• D. $100c{m}^2$

Answer 1

The correct option is C $84c{m}^2$

Let $a=13cm$, $b=14cm$ and $c=15cm$

Now, $s=\frac{a+b+c}{2}$

$=\frac{13+14+15}{2}$

$=21cm$

Area:

$△=\sqrt{s(s-a)(s-b)(s-c)}$

$=\sqrt{21(21-13)(21-14)(21-15)}$

$=\sqrt{21\times 8\times 7\times 6}$

$=\sqrt{7\times 3\times 2\times 2\times 2\times 7\times 2\times 3}$

$=2\times 2\times 3\times 7$

$=84c{m}^2$