Question

Two sides of a triangle are $13cm$ and $14cm$ and its semi-perimeter is $18cm$. Then, the third side of the triangle is:

• A. $12cm$
• B. $11cm$
• C. $10cm$
• D. 9cm

Answer 1

The correct option is D 9cm

Let $a=13cm$, $b=14cm$, $s=18cm$.

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

$\Rightarrow \frac{13+14+c}{2}=18$

$\Rightarrow c=36-27=9cm$

$\therefore$ Third side of triangle is: $9cm$