Answer
$6.3\;ft$.
Work Step by Step
The given values are.
Area $A=20\;ft^2$.
Height $=h$
Base $=h$
Formula for the area of the triangle.
$\Rightarrow A=\frac{1}{2}\times Height \times Base$
Substitute all values.
$\Rightarrow 20\;ft^2=\frac{1}{2}\times h \times h$
Multiply both sides by $2$.
$\Rightarrow 40\;ft^2=h^2$
Take the square root on both sides.
$\Rightarrow \sqrt{40\;ft^2}=\sqrt{h^2}$
Simplify.
$\Rightarrow 6.3\;ft=h$.
