Why the reasoning half deserves more time
A generic aptitude plan allocates most of its time to quantitative topics, because those have formulas and formulas feel learnable. Puzzles have no formulas, which makes them feel unteachable - so they get skipped, and then they appear in the test.
They are in fact highly teachable, but through method rather than content. Almost every analytical puzzle is solved by choosing the right representation - a grid, a table, a diagram - and then applying elimination systematically. That is a practisable skill, and practising it is what distinguishes preparation for this test from generic aptitude work.
What the test covers, and the caveat
Infosys rounds have generally emphasised logical and analytical reasoning alongside quantitative aptitude and verbal ability, with puzzle-style questions appearing more often than in some peer tests. Structures differ by role and by hiring cycle.
Confirm the current round structure, section list and timing on the official Infosys careers site before building a plan around any description - including this one. The aptitude topics themselves change slowly; how they are packaged into rounds does not.
Relations worth having automatic
| Topic | Relation | Note |
|---|---|---|
| Profit on cost price | (SP − CP)/CP × 100 | |
| Selling price after discount | MP × (1 − d/100) | |
| Combined work rate | 1/a + 1/b | days = reciprocal |
| Average | sum / count | reconstruct the sum |
| LCM × HCF | = product of the two numbers | useful check |
| Clock: hour hand | 30° per hour + 0.5° per minute | |
| Clock: minute hand | 6° per minute | |
| Speed conversion | km/h × 5/18 = m/s | |
| Successive percentages | multiply the factors | never add |
| Alligation | ratio = (far − mean) : (mean − near) | for mixtures |
The five mistakes that cost the most marks
- ✓Skipping puzzle questions as unsolvable. Most yield to a grid, and the setup is the hard part rather than the logic.
- ✓Memorising syllogism outcomes instead of drawing them. Venn diagrams handle three-statement questions that memorised rules do not.
- ✓Avoiding data interpretation because it looks time-consuming. It is often the fastest section once you read selectively.
- ✓Practising only comfortable questions to protect a high accuracy rate. Practice is where you should be getting things wrong.
- ✓Building a plan around a round structure found in an old forum post rather than the current official page.
Practice set 1: quantitative aptitude
1. An item is marked at 800 and sold at a 25% discount. If the cost price was 500, what is the profit percentage?
20%. The selling price is 800 × 0.75 = 600, so the profit is 600 − 500 = 100, and the profit percentage on cost price is 100/500 × 100 = 20%. Note the two different bases - discount is on the marked price and profit is on the cost price, and mixing them is the standard trap in this question type.
2. What is 24% of 350?
84. Decompose: 25% of 350 is 87.5, and 1% is 3.5, so 24% is 87.5 − 3.5 = 84. Working from a convenient nearby percentage and adjusting is usually faster than direct multiplication, and it is a habit worth building for mental calculation under time pressure.
3. Two numbers are in the ratio 5:7 and their sum is 96. Find them.
40 and 56. The total parts are 5 + 7 = 12, so one part is 96/12 = 8, giving 5 × 8 = 40 and 7 × 8 = 56. Checking that the two sum back to 96 takes a second and catches arithmetic slips reliably.
4. The average age of 10 people is 25. One person aged 40 leaves. What is the new average?
About 23.33. The original total is 10 × 25 = 250. Removing the 40-year-old leaves 210 across 9 people, giving 210/9 ≈ 23.33. Reconstructing the total from the average is the step that makes every question of this shape straightforward.
5. A train 200 m long travelling at 72 km/h crosses a pole. How long does it take?
10 seconds. Convert the speed first: 72 × 5/18 = 20 m/s. Crossing a pole means covering the train's own length, so the time is 200/20 = 10 seconds. Crossing a platform would require adding the platform's length to the distance, which is the usual variation.
6. A is twice as efficient as B and together they finish a job in 8 days. How long would A take alone?
12 days. If B's rate is x, A's is 2x, so together they do 3x per day, and 3x = 1/8 gives x = 1/24. A's rate is 2/24 = 1/12, so A alone takes 12 days. Efficiency questions are solved by converting the efficiency ratio into a rate ratio first.
7. In what ratio must a 20% solution be mixed with a 50% solution to obtain a 30% solution?
2:1. By alligation, the ratio is the difference from the far value to the difference from the near value: (50 − 30) : (30 − 20) = 20 : 10 = 2:1. So two parts of the weaker solution to one part of the stronger. Alligation converts most mixture questions into one subtraction each.
8. Find the LCM and HCF of 12 and 18, and verify your answer.
LCM 36 and HCF 6. Factorising, 12 = 2² × 3 and 18 = 2 × 3², so the LCM takes the highest power of each prime, 2² × 3² = 36, and the HCF the lowest, 2 × 3 = 6. Verify with the identity LCM × HCF = product of the numbers: 36 × 6 = 216 = 12 × 18. That check is worth doing every time.
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Practice set 2: logical reasoning
9. Why should syllogisms be solved with Venn diagrams rather than rules?
Because memorised rules cover only simple two-statement cases and break down as soon as a third statement or a negative premise appears. A Venn diagram tests every possible arrangement, and a conclusion follows only if it holds in all of them. Drawing takes twenty seconds and eliminates the ambiguity entirely.
10. What is the method for a linear seating arrangement?
Draw the row and place the most constrained information first - an absolute position beats a relative one. Mark what is definitely known separately from what is merely possible, and use elimination. Watch the wording: 'immediately to the left' fixes adjacency, while 'to the left' only fixes order.
11. How do you approach a blood relations question?
Draw the family tree using a consistent notation, and build it from whichever statement gives you a fixed pair. Working backwards from the question's final relationship is often quicker than working forwards from the first clue, since the question tells you which two people matter.
12. What should you look for in a coding-decoding question?
A consistent transformation - a fixed letter shift, a reversal, a positional rearrangement, or a numeric substitution. Write the alphabet positions if the pattern is not visible in letters. Testing your rule against a second given example before applying it is what prevents a plausible but wrong decode.
13. What does a data sufficiency question actually ask?
Whether the statements provide enough information, not what the answer is. So you should stop as soon as sufficiency is established rather than completing the calculation. Evaluate each statement independently first, then together - and resist using information from one while assessing the other.
14. How do you handle statement-conclusion questions?
Accept the statements as true even if they contradict common knowledge, and ask whether the conclusion follows necessarily from them alone. A conclusion that is true in the real world but not derivable from the statement is wrong. Bringing in outside knowledge is the most frequent error in this format.
15. What is the general method for a puzzle with several categories?
Draw a grid with one category per row and another per column, and fill in definite exclusions with crosses before looking for positives. Each new deduction should be recorded immediately. Most such puzzles unlock after two or three forced placements, so the work is in being systematic rather than clever.
16. How should you use constraints in an arrangement puzzle?
Rank them by how much they restrict the possibilities and apply the most restrictive first. A statement fixing an absolute position is worth more than one giving a relative order. Applying weak constraints early generates many possibilities you then have to eliminate, which is where time is lost.
Practice set 3: analytical puzzles
17. Why is choosing the right representation the hard part of a puzzle?
Because once the information is in a grid or diagram, the deductions are usually mechanical. A puzzle that seems impossible in prose often resolves in three steps when tabulated. So the practised skill is recognising which representation fits - grid for matching, line for ordering, circle for circular arrangement.
18. How does elimination work in practice?
Record what cannot be true as aggressively as what can. Crosses in a grid accumulate until a row or column has only one possibility left, which forces a placement. Beginners record only positives and stall; the negatives are what generate the forced deductions.
19. What is the approach to a cryptarithmetic problem?
Start from the leftmost column, since a carry into it means the leading digit is 1. Look for columns where the same letter appears twice, and use the constraint that no two letters share a digit. Testing exhaustively is too slow - the technique is to find the one or two columns that force a value.
20. What is the angle between the hands of a clock at 3:30?
75 degrees. The minute hand is at 30 × 6 = 180°. The hour hand is at 3 × 30 = 90° plus half a degree for each of the 30 minutes, so 90 + 15 = 105°. The difference is 180 − 105 = 75°. Forgetting that the hour hand moves during the hour is the classic error and would give 90°.
21. How do you approach dice and cube questions?
For dice, use the rule that opposite faces are fixed - identify which faces cannot be adjacent from the given views. For painted cubes, count by category: corner cubes have three painted faces, edge cubes two, face-centre cubes one, and interior cubes none. Those four counts answer most such questions directly.
22. How do you solve a numerical Venn diagram question?
Work from the innermost region outward. Fill in the number in all three sets first, then subtract to find those in exactly two, then exactly one. Filling the outer regions first double counts the overlaps, which is the standard error in this question type.
23. What should you check when a number series is not obvious?
Compute the differences, then the differences of those. If neither is regular, check ratios, then alternating patterns where odd and even positions follow separate rules, then squares, cubes and primes. Working through that checklist systematically is faster than staring at the sequence hoping for insight.
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Practice set 4: verbal ability
24. How should you handle reading comprehension efficiently?
Read the questions before the passage so you know what to look for. Most questions point to a specific paragraph, making targeted reading faster than comprehensive reading followed by searching. Answer strictly from the passage - plausible outside knowledge is a reliable trap.
25. What are the most common error-spotting categories?
Subject-verb agreement across an intervening phrase, tense inconsistency, wrong prepositions, misplaced modifiers and pronoun-antecedent mismatches. Checking agreement deliberately - identifying the actual subject, ignoring the phrase between - catches the largest single group.
26. What should you check in sentence correction questions?
Whether the corrected version changes the meaning. The grammatically cleanest option is wrong if it says something different from the original. Check parallel structure in lists, and prefer concise phrasing when two options are otherwise equivalent - but never at the cost of meaning.
27. How do you approach fill-in-the-blank questions?
Identify the logical relationship first, using connectives such as although, therefore and despite. Predict your own word before reading the options, then choose the closest match. Choosing by which word sounds most impressive is how the distractors are designed to catch you.
Practice set 5: preparation strategy
28. How should you structure preparation given the emphasis on reasoning?
Allocate more time to logical and analytical reasoning than a generic aptitude plan would suggest, without neglecting quantitative and verbal. Reasoning improves through method practice - grids, Venn diagrams, elimination - rather than through content revision, so it needs different study sessions from the quantitative topics.
29. How do you manage time on puzzle questions?
Set a limit and hold to it. A puzzle that has not started resolving within a couple of minutes usually will not, and the time is better spent on questions with a clearer path. Attempt the ones whose structure you recognise first, and return to the rest if time allows.
30. What should you confirm before finalising your preparation plan?
The current round structure, section list and timing on the official Infosys careers page for your role and cycle. Company processes change, and a plan built around a description found in an old forum thread can allocate effort to sections that no longer exist in that form.
How to prepare efficiently
- ✓Give reasoning and puzzles more time than a generic plan suggests - that is where this test differentiates.
- ✓Practise the representations explicitly: grid for matching puzzles, line for ordering, Venn for syllogisms.
- ✓Record negatives as aggressively as positives when working a grid. The crosses generate the forced deductions.
- ✓Do data interpretation regularly. It looks slow and is usually among the fastest sections once you read selectively.
- ✓Practise at a difficulty that makes you get things wrong. A comfortable accuracy rate in practice means the difficulty is too low.
- ✓Confirm the current round structure on the official portal before committing to a plan.
Turn this into active practice
Puzzles are the clearest case where reading a solution teaches almost nothing. The worked answer shows the completed grid, which hides the only difficult decision - how to set the grid up in the first place. That decision is learned by facing an unstructured puzzle and building the structure yourself.
The Infosys aptitude quiz on QUFF generates fresh questions across quantitative aptitude, logical reasoning, puzzles and verbal ability, marks them instantly and explains each answer. Do mixed timed sets, and for every puzzle you get wrong, note whether the representation or the deduction failed - the two need different practice.
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