Answer :
When I saw this, I said to myself "Self ! We don't know anything about
decagons.", and then I went searching online for stuff about decagons.
This just goes to show how stupid I can be when I don't take a little time
to THINK before I go running around screaming.
-- When you draw all the lines from the center to the vertices of the
decagon, you'll have 10 little triangles.
-- The area of the whole thing is 161 square inches, so the area of each
little triangle is 1/10 of that . . . . . 16.1 square inches.
-- The area of each little triangle is (1/2) (base) (height), just like
every other triangle.
The base is the 4.6 inches of one side of the decagon.
Area = (1/2) (base) (height)
Multiply each side by 2: 2 x area = (base) x (height)
Divide each side by (base): (2 x area) / (base) = height
Height = (2 x 16.1) / (4.6) = 7 inches .
Let that be a lesson to both of us.
THINK before you jump.
