Decimal Day use pennies or threepenny pieces, to pay them in multiples of 6d (p, the lowest common multiple of the two systems). Bus companies (at that time many state-owned by the National Bus Company) were another exception, going decimal on Sunday 21 February. Decimal Day itself went smoothly. Criticisms included the small size of the new halfpenny coin and the fact that some traders had taken advantage of the transition to raise prices. Some used new pennies as sixpences in vending machines. After 15 February, shops continued to accept payment in old coins, but always issued change in new coins. The
Cocker's Decimal Arithmetick Cocker's Decimal Arithmetick Cocker's Decimal Arithmetick is a grammar school mathematics textbook written by Edward Cocker (1631–1676) and published posthumously by John Hawkins in 1684. "Decimal Arithmetick" along with companion volume, "Cocker's Arithmetick" published in 1677, were used in schools in the United Kingdom for more than 150 years. The concept of decimal fractions and the advantages of using them in calculations were well known, but a wide variety of different notations were in use. After surveying various notations, "Decimal Arithmetick" recommends the decimal point notation introduced by John Napier: "Decimal Arithmetick" gives instructions for calculations involving decimals, methods of