Mr. Kong’s Arithmetic, Volume I

Page Three

To find the amount of glutinous rice|original: 糯米; nuòmǐ from unhusked grain|original: 米粟; mǐsù, multiply by three and divide by five.
To find unhusked grain from glutinous rice, multiply by five and divide by three.
To find cooked rice|original: 飯; fàn from glutinous rice, multiply by five and divide by two. This ratio suggests that the volume of cooked rice is 2.5 times that of the dry grain.
To find cooked glutinous rice from unhusked grain, multiply by six and divide by four.
To find glutinous rice from cooked glutinous rice, multiply by two and divide by five.
To find cooked rice from malted rice|original: 糵米; nièmǐ, multiply by eight and divide by four.

To reduce a value by one-tenth: multiply by two and divide by twenty. In modern notation, this is $\frac{2}{20}$, which simplifies to $\frac{1}{10}$. The author uses a base of 20 for these operations, likely to keep the counting rods|original: 筭; suàn in a specific alignment on the board.
To reduce by two-tenths: multiply by four and divide by twenty.
To reduce by three-tenths: multiply by six and divide by twenty.
To reduce by four-tenths: multiply by eight and divide by twenty.
To reduce by five-tenths: multiply by ten and divide by twenty.
To reduce by six-tenths: multiply by twelve and divide by twenty. The text provides a rhythmic mnemonic for calculating percentages of a total.