📑 Topics on this page (Jump to Topic):
📌 1. Order of Checks
- 1. Find consecutive differences; they may be constant, increasing or squares.
- 2. If no pattern, check the ratio (×2, ×3, ×1.5).
- 3. Mixed: ×2+1, ×3−1, ×1+1, ×2+2, ×3+3 …
- 4. If it grows fast, look for squares/cubes (n², n³, n²±n).
- 5. Two series may run alternately.
📌 2. Pattern Table
| Pattern | Example |
|---|---|
| Constant difference | 5, 9, 13, 17, 21 (+4) |
| Increasing difference | 2, 3, 5, 8, 12, 17 (+1,+2,+3,+4,+5) |
| Second difference | 1, 4, 10, 20, 35 (differences 3,6,10,15 → +3,+4,+5) |
| Multiplication | 3, 6, 12, 24, 48 (×2) |
| ×n+1 | 2, 5, 11, 23, 47 (×2+1) |
| Squares / Cubes | 1, 4, 9, 16, 25; 1, 8, 27, 64 |
| Primes | 2, 3, 5, 7, 11, 13 |
| Fibonacci | 1, 1, 2, 3, 5, 8, 13 |
⚠️ Exam Traps:
- For 'wrong term' questions, confirm the rule using at least 3 terms before picking the wrong one.
- In alternate series, odd-placed and even-placed terms follow different rules.
📌 3. Letter & Alphanumeric Series
- Convert letters to numbers (A=1 … Z=26) and solve like a number series.
- Track each position in a cluster separately: AZ, BY, CX, DW.
- Alphanumeric: A1, C3, E5, G7 — rules for both letter and number.
📌 4. Missing Number (Matrix / Figure)
- Row-wise or column-wise sum/product may be equal.
- Third number = first ⊕ second (e.g. a×b, a²+b², (a+b)×2).
- In circle/triangle figures, the outer numbers produce the inner number.
💡 Memory Tip: Check the row rule first; if not, the column, then the diagonal.
📌 5. Practice MCQs
📝 Practice MCQs (prepared by SF Prep — not PYQs)
Q1. Complete the series: 5, 9, 13, 17, ? Practice
Correct answer: (B)
Add 4 each time: 17 + 4 = 21.
Add 4 each time: 17 + 4 = 21.
Q2. Complete the series: 2, 3, 5, 8, 12, ? Practice
Correct answer: (C)
Differences +1, +2, +3, +4, +5: 12 + 5 = 17.
Differences +1, +2, +3, +4, +5: 12 + 5 = 17.
Q3. Complete the series: 2, 5, 11, 23, ? Practice
Correct answer: (D)
Rule ×2 + 1: 23 × 2 + 1 = 47.
Rule ×2 + 1: 23 × 2 + 1 = 47.
Q4. Complete the series: 1, 8, 27, 64, ? Practice
Correct answer: (A)
1³, 2³, 3³, 4³, 5³ = 125.
1³, 2³, 3³, 4³, 5³ = 125.
Q5. Complete the series: 3, 6, 12, 24, ? Practice
Correct answer: (B)
Each term ×2: 24 × 2 = 48.
Each term ×2: 24 × 2 = 48.
Q6. Complete the series: 1, 1, 2, 3, 5, 8, ? Practice
Correct answer: (C)
Fibonacci: sum of previous two terms, 5 + 8 = 13.
Fibonacci: sum of previous two terms, 5 + 8 = 13.
Q7. Complete the series: 1, 4, 10, 20, 35, ? Practice
Correct answer: (D)
Differences 3, 6, 10, 15 (next 21): 35 + 21 = 56.
Differences 3, 6, 10, 15 (next 21): 35 + 21 = 56.
Q8. Complete the series: 2, 6, 12, 20, 30, ? Practice
Correct answer: (A)
n² + n: 6² + 6 = 42 (differences 4, 6, 8, 10, 12).
n² + n: 6² + 6 = 42 (differences 4, 6, 8, 10, 12).
Q9. Find the wrong term: 4, 9, 16, 25, 35, 49 Practice
Correct answer: (B)
2², 3², 4², 5², 6², 7² — it should be 6² = 36, so 35 is wrong.
2², 3², 4², 5², 6², 7² — it should be 6² = 36, so 35 is wrong.
Q10. Complete the series: 2, 3, 5, 7, 11, ? Practice
Correct answer: (C)
Consecutive primes; after 11 comes 13.
Consecutive primes; after 11 comes 13.
Q11. Complete the series: 1, 10, 3, 9, 5, 8, ? Practice
Correct answer: (D)
Alternate: 1, 3, 5, 7 (+2) and 10, 9, 8 (−1); next term is 7 from the first series.
Alternate: 1, 3, 5, 7 (+2) and 10, 9, 8 (−1); next term is 7 from the first series.
Q12. Complete the series: 6, 11, 21, 41, ? Practice
Correct answer: (A)
×2 − 1: 41 × 2 − 1 = 81.
×2 − 1: 41 × 2 − 1 = 81.
Q13. Complete the series: A, C, F, J, O, ? Practice
Correct answer: (B)
Positions 1, 3, 6, 10, 15 (+2,+3,+4,+5); next +6 = 21 = U.
Positions 1, 3, 6, 10, 15 (+2,+3,+4,+5); next +6 = 21 = U.
Q14. Complete the series: AZ, BY, CX, ? Practice
Correct answer: (C)
First letter +1 (A, B, C, D), second −1 (Z, Y, X, W).
First letter +1 (A, B, C, D), second −1 (Z, Y, X, W).
Q15. Complete the series: A1, C3, E5, G7, ? Practice
Correct answer: (D)
Letter +2 and number +2: I9.
Letter +2 and number +2: I9.
Q16. Complete the series: Z, X, U, Q, ? Practice
Correct answer: (A)
Positions 26, 24, 21, 17 (−2,−3,−4); next −5 = 12 = L.
Positions 26, 24, 21, 17 (−2,−3,−4); next −5 = 12 = L.
Q17. Missing number: rows (2, 3, 6), (4, 5, 20), (6, 7, ?) Practice
Correct answer: (B)
Third number = first × second: 6 × 7 = 42.
Third number = first × second: 6 × 7 = 42.
Q18. Missing number: (3, 4, 25), (5, 12, 169), (6, 8, ?) Practice
Correct answer: (C)
a² + b²: 6² + 8² = 36 + 64 = 100.
a² + b²: 6² + 8² = 36 + 64 = 100.
Q19. Complete the series: 0, 7, 26, 63, ? Practice
Correct answer: (D)
n³ − 1: 1−1, 8−1, 27−1, 64−1, 125−1 = 124.
n³ − 1: 1−1, 8−1, 27−1, 64−1, 125−1 = 124.
Q20. Complete the series: 120, 99, 80, 63, 48, ? Practice
Correct answer: (A)
n² − 1: 11²−1, 10²−1, 9²−1, 8²−1, 7²−1, 6²−1 = 35.
n² − 1: 11²−1, 10²−1, 9²−1, 8²−1, 7²−1, 6²−1 = 35.