Using the formula for the area of a triangle we can solve for the base.
The formula for area of a triangle is : Area = 1/2 x base x height
We are given the area and the height:
33.6 = 1/2 x 4 x base
Multiply both sides by 2 to remove the 1/2:
67.2 = 4 x base
Divide both sides by 4 to solve for the base:
67.2 /4 = 16.8
Check: Area = 1/2 x 4 x 16.8 = 33.6
The base is 16.8 inches.