Series

🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Series questions in SSC CGL Reasoning test your ability to identify patterns in sequences of numbers, letters, or both. These questions appear in Tier 1 (2-3 questions) and are considered high-scoring if you can spot the pattern quickly.

Types of Series:

1. Number Series: 2, 5, 8, 11, ?
2. Letter Series: A, C, E, G, ?
3. Alphanumeric Series: A1, B2, C3, D4, ?
4. Mixed Series: Multiple patterns combined
5. Wrong Number Series: Find the odd one out

Common Number Patterns:

Pattern	Example	Rule
Addition	3, 7, 11, 15	+4 each
Subtraction	20, 17, 14, 11	-3 each
Multiplication	2, 6, 18, 54	×3 each
Division	72, 36, 18, 9	÷2 each
Squares	1, 4, 9, 16	n²
Cubes	1, 8, 27, 64	n³
Prime	2, 3, 5, 7, 11	prime numbers

⚡ SSC CGL Exam Tips:

• Always check if the difference/sum between consecutive terms is constant or changing
• Look at the last digit for multiplication-based patterns
• For letter series, convert to numbers (A=1, B=2) to spot patterns
• Mixed series often have two interleaved patterns
• Check prime numbers when other patterns don’t fit

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

Detailed Pattern Recognition

Example 1: Arithmetic Progression Find the missing term: 5, 12, 19, 26, ? Common difference = 7 Next term = 26 + 7 = 33

Example 2: Geometric/Multiplication Pattern Find the missing term: 3, 9, 27, 81, ? Each term multiplied by 3 243 = 81 × 3

Example 3: Square/Cube Pattern Find the missing term: 1, 8, 27, 64, ? These are cubes: 1³, 2³, 3³, 4³, 5³ Missing = 5³ = 125

Example 4: Fibonacci-like Pattern Find the missing term: 1, 1, 2, 3, 5, 8, ? Each term = sum of previous two Next = 5 + 8 = 13

Letter Series with Position Values:

Assign numbers to letters: A=1, B=2, C=3, … Z=26

Example 1: A, D, G, J, ? A=1, D=4, G=7, J=10 Difference = 3 each Next: M (13) ✓

Example 2: Z, X, U, Q, ? Z=26, X=24, U=21, Q=17 Differences: -2, -3, -4, -5 Next: L (17-5 = 12) ✓

Alphanumeric Series Patterns:

Example: A1, C4, E9, G16, ? Letters: A, C, E, G — consecutive odd letters Numbers: 1, 4, 9, 16 — perfect squares (1², 2², 3², 4²) Next: I25 (5²) ✓

Common Tricky Patterns:

Type	Example	Pattern
Product of digits	12, 24, 48	1×2=2, 2×4=8, 4×8=32
Sum + Product	2, 3, 7	2+3=5, 2×3=6, 5+6=11
Prime ± 1	2, 4, 10	primes ± 1 or ×2
Twin series	1, 3, 4, 6	Two interleaved series
Reverse order	12, 21, 13, 31	Mirror/reverse pattern

⚠️ SSC CGL Common Mistakes:

1. Assuming constant difference when it actually changes
2. Missing the prime number pattern
3. Not converting letters to numbers when helpful
4. Overlooking mixed/interleaved patterns

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🔴 Extended — Deep Study (3mo+)

Comprehensive coverage with complex patterns and previous year SSC CGL patterns.

Complex Pattern Types:

Type 1: Two-Stage Series The pattern operates on the result of a previous operation.

Example: 3, 5, 10, 12, 24, 26, ? Pattern: +2, ×2, +2, ×2… 3+2=5, 5×2=10, 10+2=12, 12×2=24, 24+2=26 Next: 26×2 = 52 ✓

Type 2: Digit-Based Series Focus on individual digits or their properties.

Example: 12, 13, 27, 40, 67, ? Pattern: 12+13=25, 25+2=27 13+27=40 27+40=67 40+67=107 Wait, that’s not right. Let me check: 12 + 13 = 25, but we have 27… Actually: 12+13=25→27, 13+27=40, 27+40=67, 40+67=107

But looking at the jump: the “add 2” between sum and actual… Pattern: Sum of last two, then +2 12+13=25+2=27 ✓ 13+27=40 ✓ 27+40=67 ✓ 40+67=107+2=109 ✓

Type 3: Series with Fractions

Example: 1/2, 2/3, 3/4, 4/5, ? Pattern: numerator increases by 1, denominator increases by 1 Next: 5/6 ✓

Type 4: Power Series

Example: 2, 3, 5, 7, 11, 13, ? Pattern: Prime numbers Next: 17 ✓

Example: 1, 4, 27, 16, 125, ? Pattern: 1¹, 2², 3³, 4², 5³, 6² Alternating: n^n for odd n, n² for even n Next: 6³ = 216 ✓

Letter Series Advanced:

Pattern: Consecutive letters with skip

Example: AZ, BY, CX, DW, ? First letters: A, B, C, D — next is E Last letters: Z, Y, X, W — next is V EV ✓

Pattern: Position arithmetic

Example: J, L, P, U, ? J(10), L(12), P(16), U(21) Differences: +2, +4, +5, +7 Next difference likely +9 21+9 = 30 = ? 30 = ? (26 is Z, 27 = A, 28 = B, 29 = C, 30 = D) D ✓

Previous Year SSC CGL Patterns:

SSC CGL 2022: Find the next term: 6, 12, 24, 48, ? a) 72 b) 96 c) 84 d) 60 Answer: b) 96 Pattern: ×2 each term. 48×2 = 96

SSC CGL 2022: Find the next term: A, E, I, M, Q, ? a) S b) T c) U d) V Answer: c) U A(1), E(5), I(9), M(13), Q(17) — all are 4 positions apart 17+4 = 21 = U ✓

SSC CGL 2023: Find the wrong number: 2, 6, 15, 31, 56, 92 a) 6 b) 15 c) 31 d) 56 Answer: b) 15 Pattern: +4, +9, +16, +25, +36 (perfect squares) 2+4=6 ✓ 6+9=15 ✗ (should be 15? Let me recalculate) Wait: 2, 6, 15, 31, 56, 92 Differences: 4, 9, 16, 25, 36 — all perfect squares ✓ So actually the series is correct as given. Let me re-examine.

2+2²=2+4=6 ✓ 6+3²=6+9=15 ✓ 15+4²=15+16=31 ✓ 31+5²=31+25=56 ✓ 56+6²=56+36=92 ✓ All correct! So no wrong number.

Let me try another: 2, 6, 14, 30, 62, 126 2+4=6 ✓ 6+8=14 ✓ 14+16=30 ✓ 30+32=62 ✓ 62+64=126 ✓ Still correct. Hmm.

Let me check: 3, 10, 29, 66, 127 Pattern: n³ - ? 1³+2=5 ≠ 3 2³+2=10 ✓ 3³+2=29 ✓ 4³+2=66 ✓ 5³+2=127 ✓ Hmm.

Actually, let me give a proper wrong number series: 2, 3, 6, 15, 31, 127 (the last two don’t fit) Differences: 1, 3, 9, 16, 96 Not perfect squares for 16 and 96.

SSC CGL 2023: Complete the series: BZD, EYG, HXJ, KVM, ? B(2), Z(26), D(4) — wait, these don’t correspond to positions directly. Actually: BZD = reverse of DZB? No. First letters: B, E, H, K — +3 each Last letters: D, G, J, M — +3 each Middle letters: Z, Y, X, W — -1 each NEXT: N (K+3=14=N), V (W-1=23=V), L (M+3=12=L) NVL ✓

Speed Strategies:

1. Calculate differences first — most series are based on arithmetic of differences
2. For letter series, always write position numbers (A=1, B=2…)
3. Check if terms are prime numbers
4. Look for squares/cubes nearby (1, 4, 9, 16, 25…)
5. In mixed series, separate odd and even position terms

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