Sixths & twelfths
Definition · Level 11 · Interview practice
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1/6 = 16.67%, 5/6 = 83.33%, 1/12 = 8.33%, 5/12 = 41.67%, 7/12 = 58.33% — the dice and calendar-month fractions.
Example
A 7 with two dice: 6/36 = 16.67%.
Where Tradecraft teaches it
Level 11 · Interview practice, in the lesson “Mental math toolkit”: Near-100 products, squares, fraction tables, compounding, square roots and basis points — the shortcuts behind fast answers.
Related terms
- √2, √3 and e≈ 1.414, ≈ 1.732 and ≈ 2.718. With independent returns, vol over two or three periods is one-period vol times the first or the second; the last is…
- √252≈ 15.87 — the factor between daily and annual volatility on trading days: annual σ = daily σ × 15.87.
- √365≈ 19.1 — the calendar-day annualisation factor, for markets that trade every day (crypto) or quantities measured over all days of the year, weekends…
- 1.05^10≈ 1.629: ten years at 5% compounded grows money by about 63%, not 50% — the benchmark for sanity-checking any compounding answer.
- Difference of squares(a + b)(a − b) = a² − b²: a product of two numbers equidistant from a round number becomes that round number squared minus a small square.
- EighthsSteps of 12.5%: 1/8 = 12.5%, 3/8 = 37.5%, 5/8 = 62.5%, 7/8 = 87.5%; halve again for 1/16 = 6.25%.