Trade math cheat sheet
Right triangle
Hypotenuse: c = √(a² + b²). A missing leg: a = √(c² − b²). The 3-4-5 (and its multiples, 6-8-10, 9-12-15) squares a corner without a square.
Area & volume
Rectangle: length × width. Triangle: ½ × base × height. Circle: π × r². Box volume: length × width × height. Cylinder: π × r² × length.
Percentages & ratios
Percent of a number: (percent ÷ 100) × number. Percent change: (new − old) ÷ old × 100. A ratio a : b scales by multiplying both sides by the same factor.
Conversions
| 1 inch | 25.4 mm (exact) |
| 1 foot | 0.3048 m (exact) |
| 1 metre | ≈ 3.281 ft |
| Fraction → decimal | top ÷ bottom |
| Decimal inch → mm | × 25.4 |
All of this is public arithmetic and geometry — nothing on this sheet is code-book data. π ≈ 3.1416.
Put it to work on the trade math practice drill, which generates fresh problems across all of the above.
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