Question

find the area of triangle which sides are 91 m 98 m and 105 m

Answer 1

When we are only provided with the sides of the triangle, we should use the Heron's Formula to find out the area of the triangle. 
The three sides of the triangle are 91 m, 98 m and 105m. 
Let $a = 91, b = 98, c = 105$. 
First, we will find out the value of $s$. 
$s = \frac{a+b+c}{2}$
⇒ $s = \frac{91+98+105}{2}$
⇒ $s = \frac{294}{2}$
⇒ $s = 147$
Now, we will find the value of this expression: $\sqrt{s(s-a)(s-b)(s-c)}$. We have to substitute the values of s, a, b, and c into this expression to find out the area of the triangle. 
$\sqrt{s(s-a)(s-b)(s-c)}$
$= \sqrt{147(147-91)(147-98)(147-105)}$
$= \sqrt{147*56(147-98)(147-105)}$
$= \sqrt{147*56*49(147-105)}$
$= \sqrt{147*56*49*42}$
$= \sqrt{16941456}$
$= 4116$
∴ The area of the triangle is 4116 $m^{2}$. 

Hope this may help you.