Online coding and Python classes in Bolton

Daniels's book gives the definition in passing: counts are "hanks in the pound". So 40's means 40 hanks weigh one pound, and 60's means 60 hanks weigh one pound. The learner first converts the prices into pence, at 12 pence to the shilling: 14 shillings is 168d and 25 shillings is 300d. Per pound, the fine yarn costs 300 / 168, or 1.79 times as much. That is the number most people stop at.

But a weaver buys thread to cover cloth, and cloth is measured by length. Dividing each price by its count gives the price per hank: 4.2d for 40's and 5.0d for 60's. Measured by length, Crompton's finer yarn cost only about 19 per cent more, even though a pound of it cost 79 per cent more. The program prints both, labels each clearly, and the learner writes one sentence saying which comparison answers which question.

The second trap is averaging. Blend 60 hanks of 40's with 60 hanks of 60's. The learner's first guess is a count of 50. The code weighs it instead: the 40's weighs 1.5 pounds, the 60's weighs 1 pound, so 120 hanks weigh 2.5 pounds, a count of 48. Averaging rates over equal lengths needs the harmonic mean, the same rule that governs average speed over equal distances. A test checks that the function returns 48, and another that an equal-weight blend correctly returns 50.

Spotting the wrong average is one strong reason for Bolton teenagers to keep learning to code in 2026. The longer argument is in why teenagers should still learn to code in 2026.