Mathematics
What the module tests
CAO Part-66 mathematics is a tool module: arithmetic, algebra, geometry and trigonometry, and graphs. Expect unit conversions, ratio and percentage, transposition of formulas, areas and volumes, and right-triangle work rather than abstract theory. It supports later modules such as electrical fundamentals and maintenance practices.
Core rules
- Work in base SI units before calculating; convert mm to m and cm² to m².
- Respect order of operations; treat a fraction bar as a bracket.
- For parallel resistors use 1/RT = 1/R1 + 1/R2; never average the values.
- Pythagoras and SOHCAHTOA solve most airframe geometry; check the calculator is in degrees.
- On a graph, gradient = change in y / change in x; interpolation between plotted points is linear.
Worked example
A 28 V DC circuit has a 12 Ω and a 6 Ω resistor in parallel, in series with 4 Ω. Find total current. Parallel: 1/RT = 1/12 + 1/6 = 1/12 + 2/12 = 3/12, so RT = 4 Ω. Total resistance = 4 + 4 = 8 Ω. I = V/R = 28/8 = 3.5 A. Check: power = 28 × 3.5 = 98 W.
Traps
Reciprocating the total instead of each resistance; mixing mm and cm; using radians; rounding too early; treating a percentage rise and fall as symmetrical; forgetting that a negative root may be physically meaningless in a quadratic.
Exam approach
Write the formula, substitute with units, then simplify. If the answer looks like a familiar prefix (mA, kPa, kN), convert it back to the asked unit before selecting.