Quantitative Aptitude / Numerical Ability
Numerical Ability tests arithmetic, simplification, number series, quadratic equations and data interpretation. For a treasury role, interest, yield and percentage-change questions carry practical weight, so learn the formulas behind them rather than memorising shortcuts alone.
Core rules
- Simple interest: SI = P × R × T / 100. Compound interest: A = P(1 + R/100)^T. For half-yearly compounding, halve the annual rate and double the periods; for quarterly, divide by four and multiply periods by four.
- Effective annual rate under half-yearly compounding is (1 + r/2)^2 − 1, not r.
- Work and pipes: take the LCM of individual times as total work, then add or subtract rates.
- Data interpretation: read the unit, base and footnote before calculating. Distinguish percentage of total from percentage-point change.
Worked example
₹10,000 is invested at 8% per annum compounded half-yearly for one year. Half-yearly rate = 4%, periods = 2. A = 10,000 × (1.04)^2 = 10,000 × 1.0816 = ₹10,816. CI = 10,816 − 10,000 = ₹816. Effective annual rate = 8.16%, not 8%.
Traps
Using 8% for a half-year instead of 4%; applying the simple-interest formula to a compound-interest question; assuming a 10% rise followed by a 10% fall returns to the original value (it leaves a 1% loss); mixing absolute values and percentages in DI; ignoring "approximately" and wasting time on exact division.
In series questions, check differences, then ratios, then squares and cubes before assuming a pattern.