Quantitative Reasoning, Basic Mathematics and Statistics
This domain tests calculation speed and the ability to choose the right base. Questions are usually applied to contribution and pension arithmetic, so the same tools reappear in different guises.
Core tools
- Percentage: part ÷ whole × 100. Distinguish a change in percentage points from a relative change in per cent.
- Coefficient: an increase of 15% multiplies by 1.15; a decrease of 15% multiplies by 0.85; an increase followed by the same decrease does not return to the starting value.
- Rule of three and proportionality, including prorata temporis and unit conversion (one month = 30 days for daily allowances).
- Statistics: mean, weighted mean, median, mode and range; frequency tables and percentages; index numbers on a base 100.
Applied to social security
- Contribution = base × rate; a weighted average is needed when several categories of workers or rates coexist.
- Pension = reference wage × 2.5% × years; survivors' shares are percentages of that pension, capped at 100%.
- IPP compensation = rate × value of the point.
Worked example
(a) Insured population rises from 12,500 to 14,375: (14,375 − 12,500) ÷ 12,500 = 1,875 ÷ 12,500 = 0.15, so +15%. (b) Weighted average rate: 60% of the payroll at 34.5% and 40% at 15% gives 0.6 × 34.5 + 0.4 × 15 = 20.7 + 6 = 26.7%. (c) Pension for 22 years at a reference wage of 72,000: 22 × 2.5% = 55%; 72,000 × 0.55 = 39,600 DZD per month.
Traps that cost marks
Adding percentages instead of multiplying coefficients; using the new value as the base when computing a rate of change; rounding intermediate results and drifting from the expected answer; mixing monthly and annual amounts; forgetting that a weighted mean needs the weights; ignoring the ceiling when the base exceeds it.
Key points
- Change in % = (new − old) ÷ old; do not confuse it with percentage points.
- Successive changes multiply coefficients, they do not add.
- Weighted mean = Σ(value × weight) ÷ Σ weights.
- Pension = reference wage × 2.5% × years, capped at 80%.
- Median resists extreme values; the mean does not.
- Keep units consistent: monthly with monthly, annual with annual.