Elementary Mathematics
Elementary Mathematics covers number system, percentages, ratio and proportion, time and work, speed and distance, interest, mensuration and basic trigonometry. The questions are usually direct but unit-sensitive.
Core formulas
- Percentage change = (change/original) × 100.
- Speed = distance/time; 1 km/h = 5/18 m/s.
- Simple interest = PRT/100; compound interest = P(1 + R/100)^T − P.
- Time and work: if A does a job in x days and B in y days, together they take xy/(x + y) days.
- Area of a circle = πr²; volume of a cylinder = πr²h.
Worked example
A 120 m train travelling at 54 km/h crosses a 180 m platform. Convert speed: 54 × 5/18 = 15 m/s. Total distance to clear the platform = 120 + 180 = 300 m. Time = 300/15 = 20 s.
Traps that cost marks
Forgetting to add train length to platform length, using km/h directly with metres, and mixing simple with compound interest are common. In time-and-work problems, convert days to work-per-day before adding rates. In mensuration, check whether the question asks for curved surface area or total surface area.