No pain, no gain.
In chapter 2, "The Pool of Tears", Alice tries to perform multiplication but produces some odd results: "Let me see: four times five is twelve, and four times six is thirteen, and four times seven is—oh dear! I shall never get to twenty at that rate!" This explores the representation of numbers using different bases and positional numeral systems: 4 × 5 = 12 in base 18 notation, 4 × 6 = 13 in base 21 notation, and 4 × 7 could be 14 in base 24 notation. Continuing this sequence, going up three bases each time, the result will continue to be less than 20 in the corresponding base notation. (After 19 the product would be 1A, then 1B, 1C, 1D, and so on.)
en.wikipedia.org/wiki/Alice_in_wonderland#Symbo...
en.wikipedia.org/wiki/Alice_in_wonderland#Symbo...