What is the length to the nearest tenth of the altitude of an equilateral triangle with a perimeter of 30 inches

Each side of an equilateral triangle = perimeter / 3.

Each side = 10 inches.

The altitude divides the triangle into two 30 60 90 triangles. The hypotenuse is 10 inches and the short side is 5 inches.

altitude^2 = 10^2 - 5^2

altitude^2 = 100 - 25

altitude^2 = 75

altitude = 8.6602540378