Help with maths please
 

I have to make a lot of HST the pattern says cut strips 1/78 recut into 1/78 squares you understand that method I would like to be able to use the method where you make 8 at a time, how big would I need to cut the squares to use this method, will these HST be 1.5 square when finished?
Thank you

They will be 1" when finished, 1.5" before you sew it into the quilt.
To do multiples, look up the grid technique. Here's one example.
http://quiltsbyjen.ca/how-to-make-ha...s-with-a-grid/

There are other techniques out there to make multiples.

And be sure you use scant 1/4 inch seam or they might not end up them exact size you need. Test a few before you sew a lit to make sure the seam allowance is correct.

The 1/78 you are using is NOT what you mean. That figure would be too little to see much less use. Are you saying 1 7/8? (1.875)

There's a wonderful tutorial here on the quilting board: http://www.quiltingboard.com/tutoria...s-t141047.html I'm a little unsure as to the finished size you need. Are you trying to make 1.5" HSTs?

First are the HST only in 2 colors. If so you are good to go making the 8 at once.

If they are to be scrappy then you might want to consider something like Thangles or just cut squares and do the diagonal sewing per the formula.

I make 8 at a time by using 2 sqs right sides togather. Draw an x and sew on both sides of line 1/4 in. Cut in half both ways then on lines. They will need a small amt of trimming. For one and a half inch triangles you will need the squares to be 4 inchs. For two and a half in triangles use 6 in sqs and for three and a half use 8 in squares.
I also use Quilt in a Days triangle square up ruler that only requires one cut to square up. It is worth the price for the ruler.

You could also use products like THANGLES or TA-DA In my opinion useing one of these products is the only way to go.