Question

Two sides of a triangle are $12\text{cm}$ and $14\text{cm}$. The perimeter of that triangle is $36\text{cm}$. What is the length of the third side?

Answer 1

Step 1: Let the length of the third side be $s$. The perimeter of the triangle is the sum of all the lengths of the triangle.

$\begin{array}{rcl}12+14+s& =& 36\end{array}$

Step 2: Transpose the numbers on the right side and solve for $s$.

$\begin{array}{rcl}s& =& 36-12-14\\ & =& 10\text{cm}\end{array}$

Hence, the the length of the third side is, $10\text{cm}$.