Question

find the percentage increase in the area of a triangle if it's each side is tripled

Answer 1

Using Heron's formula,
$area = \sqrt{s(s - a)(s - b)(s - c)}$
If each side is trippled, the each term in the formula s, (s-a), (s-b), and (s-c) trippled. Since they are under square root, area becomes 9 times. i.e., increase in area is 8 times.
Therefore, percentage increase in area is
800%