Quantitative Aptitude / Numerical Ability
Quantitative Aptitude / Numerical Ability tests speed and accuracy across arithmetic, algebra and basic data handling. HARCO Bank Clerk questions are usually short, so the mark is won by choosing the right method, not by long calculation.
Core rules
- Follow BODMAS: simplify brackets first, then powers/roots, division/multiplication, addition/subtraction.
- Percentage change = (change/original) x 100. For successive changes use multipliers: +10% then -10% gives 1.10 x 0.90 = 0.99, a net 1% fall.
- Average = sum/count; if every item rises by k, the average rises by k.
- SI = PRT/100; CI = P[(1+R/100)^T - 1] for annual compounding.
- Work: combined rate = sum of individual one-day rates. Speed: distance = speed x time; convert km/h to m/s by multiplying 5/18.
Worked example
A sum of ₹12,000 earns 10% p.a. compound interest for two years. Find CI. Year 1 interest = 1,200; amount = 13,200. Year 2 interest = 10% of 13,200 = 1,320. CI = 1,200 + 1,320 = ₹2,520. Shortcut: 12,000 x (1.1^2 - 1) = 12,000 x 0.21 = ₹2,520.
Traps
Mixing simple and compound interest; using the new value as the denominator in percentage change; forgetting that "A is 20% more than B" means A = 1.2B, not B = 1.2A; ignoring units in speed and mensuration; over-calculating when options are far apart.