I am trying to make a star block.
the 5 pieces I have cut are 5 squares that are all 6 and 1/2 inches sq.
there is one for each corner and one for the center.

Now for the last 4 blocks that I need help with
they are 2 colors and are made of 4 triangles.
Each triangle has the top point of the triangle meeting in the center and the color is every other one. so when placed in the last 4 spots in the block these 4 blocks make the star points.
So basically it is a 9 patch and each of the 9 blocks have to measure 6 1/2 sq before sewn together.

My problem is I dont know what size triangles to cut so when they are all sewn together they equal 6 and 1/2 inch blocks?
Math was not my stong point.

Do you understand what I am saying....I think the block is called teh Ohio Star and if you click on this link you can see what I am trying to make. I just dont know how to do the math...

http://www.quilterscache.com/O/OhioStarBlock.html

I know I can make a paper 6 1/2 inch block and cut it into 4 pieces and add 1/2 inch but is that right? or will it short me?
My brain is to tired and I need help. Thanks in advance.