Q7 Q30.) Find the area of the triangle specified below.

When you have the side lengths of a triangle, you can use Heron's Formula to find the area of a triangle. 

Heron's Formula: [tex] \sqrt{p(p - a)(p - b)(p - c)} [/tex]
where p is half the perimeter.

Find half the perimeter: 19 + 21 + 15 = 55
                                          55/2 = 27.5 meters

Plug the numbers in to the formula.

[tex] \sqrt{27.5(27.5- 19)(27.5- 21)(27.5- 15)} [/tex]

Now solve (I would recommend using a calculator).

[tex] \sqrt{27.5(27.5- 19)(27.5- 21)(27.5- 15)} [/tex] = 137.8
137.8 rounded to the nearest meter is 138.

A = 138 square meters