Quote Originally Posted by Sheena View Post
At first I thought you might be able to use a jelly roll too, but you can't unless you trim your charms.

So lets say you're going to use the charms as they are.

For the four side square you need four pieces of colour A (yellow) and four of colour B (orange) . Each piece must measure 2 3/4" x 5". Sew one A and one B together and sew the yellow side to the charm.

You now need to know how wide to cut a strip of blue fabric.

The blue diagonals on the corner are more tricky and you need Pythagoras's Theorum which is "The square on the hypotenuse is equal to the sum of the squares on the other two sides." This will let you know how wide a strip to cut.

The hypotenuse is the side of a right angled triangle that is opposite the right angle.

In the corner square, the blue fabric meets the yellow fabric where the yellow fabric goes horizontal and vertical. You know that where the blue meets the yellow this is 2 1/4" long.

Back to Pythagorus - so the horizontal yellow piece is 2 1/4" when sewn to the blue and the charm,

to find the square of a number you multiply it by itself so 2 1/4 x2 1/4 = 5.06 "

The vertical yellow piece is also 2 1/4 " so it's square is also 5.06"

The sum of 'the other two sides' is therefore 10.12"

So the square of the hypotenuse is the square of 10.12" , which is 3.18"

The blue strip needs to be 3.18" wide and seam allowance of 2 x 1/4" ie 1/2" or 0.5" , so that's 3.68". This is 3 7/10" to the nearest single decimal point.

Problem: We don't work in 10th of an inch we work in 8th of an inch.
Answer: 3 7/10" we can say is 3 6/8".

You need to cut a blue strip 3 6/8" wide.

CAN ANYONE CHECK THIS PLEASE.
I think you might be a little off - I was taught Pythagoreum's theorum to be a^2 + b^2 = c^2. So if you're looking at the orange triangles on the corner blocks, it would be 2.5^2 + 2.5^2 = c^2 => 6.25+6.25=c^2 => 12.5=c^2 => 3.5355=c. My math is based on charm squares, not on 4" squares, but you will hopefully get the idea.

BUT in terms of quilting, can't you just take a 2.5" square and snowball the edges to get the same effect? I don't think the diagonal in this case matters, since it is incorporated into a square.