Arithmetic for idiots*

Last night in an effort to stop me fretting about whether I would have enough time remaining to finish the Peacock Feathers shawl before December 9th the boyfriend demonstrated how to calculate how many stitches remain in a triangular piece of knitting.

Take the number of stitches on your current row (A) and subtract from the number of stitches on your final row (B). Divide this number by 2 and add to (A). Multiply this number by the number of rows you still have to knit (C).

or:

((B - A)/2 + A) x C

In my case:

A = 346 (number of stitches on current row)
B = 495 (number of stitches on final row)
C = 75 (rows left to knit)

so:

495 - 346 = 149

149/2 = 74.5

346 + 74.5 = 420.5 **

420.5 x 75 = 31537.5 stitches remaining.

I think I was happier not knowing!

You can also use this to calculate how far you are through a triangular piece percentage-wise (no more guessing on Ravelry). So:

Starting number of stitches = 3
Final number of stitches = 495
Total number of rows = 250

((495 - 3)/2) x 250 = 61500

(31537/61500) x 100 = 51% left

I've not even reached the halfway mark - should I just give up now?!

By my reckoning I need to put in at the very least 20 hours of solid knitting in the next ten days. The only chink of light is that it looks like there may be an option to skip rows 191 to 222 of chart 7, curtailing the "big feathers" portion of the shawl and move straight onto the edging chart. Luckily it's my lace-knitters anonymous (a.k.a. the Oxford Bluestockings) meeting tonight so I can get some expert advice and find out if this is really a viable option.

* by which I mean a knitter who takes on a complex piece of lace knitting to a tight deadline without checking how many stitches she will have by the final row of the piece.

** this is your average number of stitches per row (in case you're interested)