Infosys Aptitude & Pseudocode — Set 1

25 Infosys-drive-style questions — quantitative aptitude, logical puzzles, verbal ability and the pseudocode round.

Quantitative Aptitude25 questionsInstant feedback + explanationsup to ≈150 XP

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Practice sheet: all 25 questions

Prefer reading first? Every question from this practice set, with the answer and a worked explanation. (Solving them in the practice set above earns XP — up to ≈150.)

Q1. The price of a book is increased by 20% and then decreased by 20%. What is the net change in price?
- a. No change
- b. 4% decrease
- c. 4% increase
- d. 2% decrease
Show answer & explanation

Answer: B. 4% decrease

Successive changes multiply: 1.20 × 0.80 = 0.96, a 4% decrease. Shortcut for +x% then −x%: net change = −x²/100 = −4%. Equal up-and-down percentage changes never cancel out.
Q2. A 40-litre mixture has milk and water in the ratio 7 : 3. How much water must be added to make the ratio 7 : 5?
- a. 6 litres
- b. 8 litres
- c. 10 litres
- d. 12 litres
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Answer: B. 8 litres

The mixture has 28 L milk and 12 L water. Milk stays fixed at 28 L = 7 parts, so 1 part = 4 L and the target water is 5 × 4 = 20 L — add 20 − 12 = 8 L. Anchor on the component that doesn't change.
Q3. 12 workers can finish a project in 20 days. After 5 days, 4 workers leave. In how many total days is the project finished?
- a. 25 days
- b. 27.5 days
- c. 28.5 days
- d. 30 days
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Answer: B. 27.5 days

Total work = 12 × 20 = 240 worker-days. In 5 days, 12 workers finish 60, leaving 180 for the remaining 8 workers: 180 ÷ 8 = 22.5 days. Total = 5 + 22.5 = 27.5 days. Converting to worker-days makes workforce changes mechanical.
Q4. How many 3-letter arrangements (with or without meaning) can be formed from the letters of WORD, without repetition?
- a. 12
- b. 24
- c. 36
- d. 64
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Answer: B. 24

Choose and arrange 3 of the 4 distinct letters: ⁴P₃ = 4 × 3 × 2 = 24. Order matters here (arrangements), so it's a permutation, not a combination — the exam tests exactly this distinction.
Q5. Two dice are thrown together. What is the probability that the sum of the numbers is 9?
- a. 1/6
- b. 1/9
- c. 1/12
- d. 5/36
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Answer: B. 1/9

Favourable outcomes: (3,6), (4,5), (5,4), (6,3) — 4 out of 36 total, which is 1/9. Sums with two dice peak at 7 (6 ways) and fall off by one way per step: sum 9 has 4 ways.
Q6. What is the compound interest on ₹10,000 at 10% per annum for 2 years, compounded annually?
- a. ₹2,000
- b. ₹2,100
- c. ₹2,200
- d. ₹2,050
Show answer & explanation

Answer: B. ₹2,100

Effective 2-year rate at 10% is 10 + 10 + (10×10)/100 = 21%, so CI = ₹2,100. The a + b + ab/100 shortcut beats computing (1.1)² and subtracting — and the ₹100 over simple interest is exactly interest-on-interest.
Q7. A boat's speed in still water is 12 km/h and the stream flows at 3 km/h. How long does the boat take to travel 45 km downstream?
- a. 3 hours
- b. 3.75 hours
- c. 4 hours
- d. 5 hours
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Answer: A. 3 hours

Downstream speed = 12 + 3 = 15 km/h, so time = 45 ÷ 15 = 3 hours. Downstream adds the stream's speed, upstream subtracts it — mixing these up is the classic error, so write both speeds down first.
Q8. The sum of the ages of a father and son is 60 years, and the father is three times as old as the son. How old is the son (in years)?

Show answer & explanation

Answer: 15

If the son is S, the father is 3S, and S + 3S = 60 gives S = 15. With "x times as old" statements, one variable is always enough — express everyone in terms of the youngest person.
Q9. Find the next term: 2, 6, 12, 20, 30, ?
- a. 36
- b. 40
- c. 42
- d. 44
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Answer: C. 42

The differences grow by 2 each time (4, 6, 8, 10), so the next difference is 12 and the answer is 30 + 12 = 42. Equivalently the nth term is n(n+1): 1×2, 2×3, …, 6×7 = 42.
Q10. If PLANT is coded as QMBOU, how is TREES coded?
- a. USFFT
- b. UTFFT
- c. USFTT
- d. USEFT
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Answer: A. USFFT

Every letter shifts one step forward (P→Q, L→M, …). Applying +1 to TREES: T→U, R→S, E→F, E→F, S→T — USFFT. Verify the shift on two letters of the given pair before applying it.
Q11. In a class, Ravi ranks 7th from the top and 26th from the bottom. How many students are in the class?
- a. 31
- b. 32
- c. 33
- d. 34
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Answer: B. 32

Total = rank from top + rank from bottom − 1 = 7 + 26 − 1 = 32; the −1 stops Ravi being counted twice. Forgetting it and answering 33 is the standard trap — the setter always includes that option.
Q12. What is the angle between the hour and minute hands of a clock at 3:30?
- a. 75°
- b. 80°
- c. 85°
- d. 90°
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Answer: A. 75°

Use |30H − 5.5M| = |30×3 − 5.5×30| = |90 − 165| = 75°. The insight behind the formula: the hour hand isn't at 3 anymore — it has drifted half a degree per minute, 15° by half past.
Q13. If 1 January 2024 is a Monday, what day of the week is 1 March 2024?
- a. Thursday
- b. Friday
- c. Saturday
- d. Sunday
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Answer: B. Friday

2024 is a leap year, so January (31) + February (29) = 60 days; 1 March is 60 days after 1 January. 60 mod 7 = 4, and Monday + 4 = Friday. Only the remainder mod 7 matters — never count weeks.
Q14. A is B's brother, C is A's mother, and D is C's father. How is A related to D?
- a. Son
- b. Grandson
- c. Nephew
- d. Brother
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Answer: B. Grandson

D is the father of C, and C is A's mother — so D is A's maternal grandfather, making A his grandson (A is male, being B's brother). Build the family tree top-down; the gender clue "brother" fixes the final answer.
Q15. A person facing east turns 90° clockwise, then 180° anticlockwise. Which direction is the person facing now?
- a. North
- b. South
- c. East
- d. West
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Answer: A. North

East turned 90° clockwise is south; south turned 180° (either way) is north. Net rotation: 90° clockwise − 180° = 90° anticlockwise from east = north. Tracking the net angle avoids stepping through each turn.
Q16. Find the odd one out: 121, 144, 169, 190.
- a. 121
- b. 144
- c. 169
- d. 190
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Answer: D. 190

121, 144 and 169 are perfect squares (11², 12², 13²); 190 is not (13² = 169, 14² = 196). Odd-one-out numbers usually hide a square, cube or prime pattern — test those three first.
Q17. Statements: All engineers are graduates. No graduate is illiterate. Conclusions: I. No engineer is illiterate. II. Some graduates are engineers. Which conclusion(s) follow?
- a. Only I follows
- b. Only II follows
- c. Both I and II follow
- d. Neither follows
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Answer: C. Both I and II follow

I: engineers sit inside graduates, and graduates are disjoint from illiterates, so engineers are too. II: "All engineers are graduates" converts to "some graduates are engineers" (valid in exam syllogism convention). Chain the sets with a quick Venn sketch.
Q18. Choose the word closest in meaning to OBSOLETE.
- a. Modern
- b. Outdated
- c. Rare
- d. Useless
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Answer: B. Outdated

Obsolete means no longer in use because something newer replaced it — outdated. "Useless" is the trap: an obsolete thing may still work fine; it's just been superseded (floppy disks still function).
Q19. Choose the word opposite in meaning to VERBOSE.
- a. Wordy
- b. Concise
- c. Loud
- d. Vague
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Answer: B. Concise

Verbose means using more words than needed; the opposite is concise — saying much in few words. "Wordy" is a synonym planted as a trap; "loud" confuses verbosity with volume.
Q20. Spot the error: "Each of the students (a) / have submitted (b) / the assignment. (c) / No error (d)"
- a. Each of the students
- b. have submitted
- c. the assignment
- d. No error
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Answer: B. have submitted

"Each" is singular and needs "has submitted". The plural "students" right before the verb is bait — with each/either/neither + "of the <plural>", the verb still agrees with the singular pronoun.
Q21. The idiom "to bite the bullet" means:
- a. To act aggressively
- b. To face a painful situation with courage
- c. To make a hasty decision
- d. To take revenge
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Answer: B. To face a painful situation with courage

To bite the bullet is to brace yourself and endure something unpleasant that can't be avoided — courage, not aggression. The phrase comes from soldiers biting a bullet during field surgery before anaesthesia.
Q22. Pseudocode: x = 10, y = 3. What does print(x mod y + x div y) output? (div is integer division)
- a. 3
- b. 4
- c. 5
- d. 6
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Answer: B. 4

10 mod 3 = 1 (remainder) and 10 div 3 = 3 (quotient), so the output is 1 + 3 = 4. Infosys pseudocode leans on mod/div pairs — remember: mod gives what's left, div gives how many times.
Q23. Pseudocode: count = 0; for i = 1 to 20: if (i mod 3 = 0 AND i mod 2 = 0) then count = count + 1. What is count at the end?
- a. 2
- b. 3
- c. 4
- d. 6
Show answer & explanation

Answer: B. 3

Divisible by both 3 and 2 means divisible by 6: within 1–20 that's 6, 12 and 18 — count = 3. Collapsing an AND of divisibility tests into one LCM test is faster and safer than scanning all 20 values.
Q24. Pseudocode: function f(n): if n <= 1 return 1 else return n * f(n − 1). What does f(5) return?
- a. 60
- b. 100
- c. 120
- d. 125
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Answer: C. 120

This is the factorial recurrence: f(5) = 5 × 4 × 3 × 2 × 1 = 120. Spotting the pattern (n × f(n−1) with base 1) beats tracing the stack call by call — name the recurrence, then compute.
Q25. Array A = [4, 8, 15, 16, 23, 42] with 0-based indexing. What is A[2] + A[4]?
- a. 31
- b. 38
- c. 39
- d. 58
Show answer & explanation

Answer: B. 38

With 0-based indexing, A[2] = 15 and A[4] = 23, so the sum is 38. The planted wrong answer 39 (= 16 + 23) comes from slipping into 1-based counting on one of the indexes — always confirm the indexing base first.