Mathematics and Quantitative Aptitude
Arithmetic
Quantitative Aptitude rewards correct set-up. Percentage change = [(new − old)/old] × 100; average = sum/count; simple interest = P × R × T/100; compound amount = P(1 + R/100)^T. In ratio problems, keep units and total parts consistent. For profit and loss, use cost price as the base unless the question says otherwise.
Mensuration
Rectangle area = l × b; triangle = ½ × base × height; circle = πr²; circumference = 2πr; cuboid volume = l × b × h; cylinder volume = πr²h. For a uniform border inside a rectangle, subtract twice the width from each side.
Data interpretation
Read the title, units and footnotes first. Compute only the required value; do not total every row unless asked. Check whether percentages are of the total or of a subgroup.
Worked example
A 40 m × 30 m field has a 2 m wide path inside its boundary. Outer area = 40 × 30 = 1200 m². Inner dimensions = (40 − 4) × (30 − 4) = 36 × 26 = 936 m². Path area = 1200 − 936 = 264 m². The key step is subtracting 2 m on each side, so 4 m from each dimension.
Traps
Forgetting unit conversion; applying simple interest when compounding is stated; using the outer dimension as the inner one; and reading a bar graph's axis scale as starting at zero when it does not.