From this concrete example may be derived a formula which can be applied to all cases where the sufficient particulars are given, and following the above example we obtain—
Example 12.—
| Courses per in. × width × length × take-up | |
| = weight in lb. | |
| counts × basis |
In this statement let the courses per inch or the sett be represented by S, the width by w, and the weight by W, counts = C, basis = B, length = L, from which we obtain the following equation—
Example 13.—
| S × w × L × T | |
| = W, | |
| C × B |
or-
S × w × L × T = W × C × B.
From this it follows that given any six of the seven factors we may obtain the seventh by substitution of values. Some of these possibilities are of academic interest only and are seldom required in practice, but a few examples may be given of the use of this formula.
Example 14.—Find the weight of 200 yd. of knitted webbing worked from 2/40's cashmere yarn with 28 courses per inch to a width of 48 in. with a take-up of 1·75.