Reasoning and Mental Ability
The question types
Number and alphabet series, analogies, coding-decoding, blood relations, direction sense, order and ranking, syllogisms, seating arrangement, and non-verbal figures where included.
Working rules
- Number series: test differences first, then ratios, then squares and cubes, then alternating patterns.
- Coding-decoding: map letter positions (A = 1 to Z = 26) and test shifts such as +1, -1, +2, -2 before assuming a reversal.
- Blood relations: draw a small family tree and mark gender with a symbol; never solve in your head.
- Direction sense: sketch the path; a left turn after moving south points east.
- Syllogism: use Venn diagrams; a 'possibility' conclusion can hold even when the certain ones do not.
- Order and ranking: total = position from left + position from right - 1.
Worked example (series)
'Find the next term: 3, 8, 15, 24, 35, ?' Reasoning: the differences are 5, 7, 9, 11, consecutive odd numbers, so the next difference is 13 and the term is 35 + 13 = 48. The terms also fit n squared minus 1 (2 squared minus 1 = 3, 3 squared minus 1 = 8), and 7 squared minus 1 = 48 confirms the answer.
Worked example (ranking)
'In a row, Ravi is 12th from the left and 18th from the right. How many people are in the row?' Reasoning: total = 12 + 18 - 1 = 29, subtracting one because Ravi is counted twice.
Traps
- Forgetting to subtract 1 in ranking problems, which double-counts the person.
- Assuming a coded word keeps its letters in the same order.
- Ignoring the possibility of negative or fractional terms in a series.
- Solving blood-relation puzzles without recording gender, then calling a sister a brother.