Two digit cubes that show every date of a month
Question
You have two blank cubes and may write one digit on each of their twelve faces. Placed side by side, the cubes must be able to display every day of a month as a two-digit number, from up to . How should the faces be labelled?
Short answer
Cube one: ; cube two: , with the turned upside down to serve as . Dates and force and onto both cubes, and – force onto both as well, leaving only six free faces for the seven digits –. The trick is that one face can read as either or .
Adapted from Zhou, A Practical Guide to Quantitative Finance Interviews, sec. 2.3 Thinking Out of the Box, 'Calendar cubes', p.10; question and answer rewritten by SelfMadeQuant.com.
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