Reasoning and Quantitative Aptitude
Reasoning and Quantitative Aptitude tests logical deduction and numerical problem solving under time pressure.
Core rules
- Series: check differences, ratios, squares/cubes, alternating patterns, and digit operations.
- Coding-decoding: map letters by position, reversal, or shifts; blood relations: draw a family tree; directions: use a coordinate sketch.
- Syllogism: use Venn diagrams; seating: fix one anchor and arrange left/right consistently.
- Arithmetic: percentage change, ratio, average, time-work, speed-distance-time, simple/compound interest, mensuration, and data interpretation.
- Time-work: if A does a job in x days and B in y days, together time=xy/(x+y).
Worked example
Two pipes fill a tank in 12 h and 18 h. Together rate=1/12+1/18=(3+2)/36=5/36 tank/h. Time=36/5=7.2 h, i.e. 7 h 12 min. The trap is to average 12 and 18, which is wrong because rates add, not times.
Traps
Do not add successive percentage changes directly; 20% then 10% is 1.2×1.1=1.32, not 30%. Convert units before speed or area calculations. In syllogism, do not assume converse statements. In seating, confirm facing direction.