Chapter 8, Problem 4SAP

To determine

To find: correct option that cannot be the length of third side of the triangle.

Explanation of Solution

Given information:

Let the sides of triangle be $a,b\text{ and }c$ .

  $\begin{array}{l}a=40\\ b=80\end{array}$

The options are as follows:

1. 40
2. 41
3. 50
4. 80
5. 81

Calculation:

The sum of two sides of triangle should be greater than the third side, so $b-a<c<a+b$ . Evaluate the value of $c$ as follows:

  $\begin{array}{c}b-a<c<a+b\\ 80-40<c<40+80\\ 40<c<120\end{array}$

Since, the value of $c$ cannot be equal to 40. So, option A. is correct.