Reasoning and Quantitative Aptitude
What is tested
Number series, percentages, ratio and proportion, averages, profit and loss, simple interest, time and work, plus verbal reasoning - coding-decoding, blood relations, direction sense, syllogism, seating arrangement and data interpretation. Speed comes from recognising the type, not from long calculation.
Core rules
Percentage change = (change ÷ original) × 100. Average = sum ÷ number of items. If a ratio is a : b, the parts are ax and bx for some x. In syllogism, draw the smallest possible Venn diagram and test whether the conclusion holds in every case. In direction problems, fix the starting point and turn clockwise or anticlockwise as stated.
Worked example
An AWC has 45 enrolled children, of whom 60 per cent are girls. Three more girls join. What percentage of the children are now girls? Reasoning: girls initially = 0.60 × 45 = 27; boys = 18, unchanged. After joining, girls = 30 and total = 48. Percentage = 30 ÷ 48 × 100 = 62.5 per cent. Note the denominator changes too - a common slip.
Traps
Ignoring the word "not" in syllogism and inequality questions; using the old total after a change; confusing percentage points with per cent; assuming data is sufficient when it is not; spending too long on one puzzle instead of securing easy marks first.