Answer: The correct answer is option (A) 60,000 ft.
Step-by-step Explanation: In a triangle with all three sides given and no vertical height, we shall not apply the conventional (commonly used) formulae which is
Area = 1/2 B x H
Rather we shall apply the Heron’s Formulae which states as follows;
Area = [square root] s(s - a)(s - b)(s - b)
Where a, b and c are the three sides and a is the semi-perimeter.
We shall start with the semi-perimeter which is
s = (300 + 400 + 500)/2
s = 1200/2
s = 600
Therefore applying the Heron’s formula, the area is calculated as
A = [square root] 600(600 - 500)(600 - 400)(600 - 300)
A = [square root] 600 (100)(200)(300)
A = [square root] 3600000000
A = 60000
The area of the given triangle is 60,000 ft.