General Mathematics and Mental Ability
Arithmetic core
Expect percentage, profit and loss, ratio and proportion, average, simple and compound interest, time-speed-distance, time and work, and mixtures. Learn the standard formulas and, more importantly, the shortcut relations: profit percent is always on cost price unless stated; successive percentage changes combine as a + b + ab/100; average speed for equal distances is the harmonic mean 2xy/(x+y), not the simple average.
Mental ability
Series completion, analogy, coding-decoding, blood relations, direction sense, ranking, clocks and calendars, and odd-one-out are common. For series, check differences, then ratios, then squares and cubes. For direction questions, draw a small compass sketch and mark each turn. For blood relations, draw a family tree with gender symbols.
Geometry and data
Know area and perimeter of standard figures, Pythagoras, angle sums, and simple interpretation of tables and bar charts. Percentage-of-total questions on a chart are frequent.
Traps
Unit mismatches (metres vs kilometres, months vs years), percentage taken on selling price instead of cost price, and ‘average of averages’ errors are classic. In coding questions, the letter shift may run backwards or alternate.
Rule of thumb
Write the known quantities with units, convert everything to one unit, then solve; most errors are unit errors, not algebra errors.
Worked example
A man travels 60 km at 30 km/h and returns at 60 km/h. Simple average would wrongly give 45 km/h. Using 2xy/(x+y) = 2×30×60/90 = 40 km/h, which is correct because equal distances are covered.