General Mathematics / Quantitative Aptitude
What is tested
Quantitative Aptitude here is speed arithmetic: number system, percentage, ratio, average, profit and loss, simple and compound interest, time-work, time-speed-distance, mensuration, basic trigonometry and data interpretation. The maths is school-level; marks go to whoever turns a question into one clean equation fastest.
Core rules
- Successive percentage changes of a% and b% give a + b + ab/100.
- Discount acts on marked price; profit acts on cost price. Marked price × (1 − d) = cost × (1 + p).
- Average speed over equal distances is the harmonic mean 2xy/(x+y), never (x+y)/2.
- SI = PRT/100; CI = P[(1 + R/100)^n − 1].
- Work: take total work = LCM of individual days; efficiency is inversely proportional to time.
- Mensuration: cylinder volume πr²h and curved surface 2πrh; cone volume ⅓πr²h; sphere volume 4/3 πr³.
- Trigonometry: tan θ = height/distance; standard values for 30°, 45°, 60° must be instant.
Worked example
A finishes a job in 12 days, B in 18 days. They work together for 4 days, then A leaves. How long does B need? Total work = LCM(12, 18) = 36 units. A does 3 units/day, B does 2 units/day; together 5. In 4 days they finish 20 units, leaving 16. B alone at 2 units/day needs 16/2 = 8 days.
Traps
Applying discount to cost price instead of marked price; treating CI as simple for the second year; adding average speeds; forgetting 1 m² = 10,000 cm²; assuming successive discounts of 10% and 20% equal a flat 30%.