29750840 = 35·41 counts.
From this we get the formula:—
7000 × yards weighed840 × counts = counts.
This is a very useful formula, as when only a small piece of cloth is available to be tested it is necessary to get as near as possible to the counts from weighing sometimes only 10 or 15 yards, or any odd length.
A calculation may occur in the following form:—
How many grains should 16 yards of 20’s cotton weigh?
There are 840 × 20 = 16,800 yards of 20’s in 1 lb., or 7000 grains.
Then if 16,800 yards weigh 7000 grains, how many grains will 16 yards weigh?
yards