Compulsory Mathematics (अनिवार्य गणित): Method, Formula and Units
Compulsory Mathematics (अनिवार्य गणित)
The SEE Compulsory Mathematics paper tests sets, arithmetic, algebra, geometry, trigonometry, mensuration, statistics and probability. Marks are awarded for method as well as answer, so show the formula, substitution and unit in every solution.
Core rules
- Sets: n(A∪B) = n(A) + n(B) − n(A∩B); use a Venn diagram when two or three sets overlap.
- Algebra: factorise by grouping; for ax² + bx + c, find two numbers whose product is ac and sum is b.
- Geometry: write the given, to prove and construction; cite theorems by statement, not just number.
- Trigonometry: in a right triangle, tan θ = opposite/adjacent; angle of elevation is measured upward from the horizontal.
- Mensuration: keep units consistent; convert cm to m before calculating area or volume.
- Statistics: mean = Σfx/Σf for grouped data; probability = favourable outcomes/total outcomes.
Worked example
Find the compound interest on Rs 20,000 for 2 years at 10% per annum compounded annually. A = P(1 + r/100)^t = 20,000(1 + 10/100)² = 20,000 × 1.21 = Rs 24,200. CI = A − P = 24,200 − 20,000 = Rs 4,200. Reasoning: compound interest adds each year’s interest to the principal, so the multiplier 1.1 is applied twice, not added as simple interest.
Traps
- Using simple interest for a compound interest question.
- Forgetting to convert units before substituting into a formula.
- Rounding intermediate values and losing accuracy.
- Drawing a diagram not to scale and then reading a length from it.
- Giving a probability greater than 1 or a negative area.