SSC CGL Reasoning: Letter-Cluster & Number Series (Real PYQ Questions)

Letter-Cluster analogy and Number Series are among the highest-frequency Reasoning sub-topics in SSC CGL Tier 1, based on our full dataset analysis. This article compiles real, verified questions from both categories, extracted directly from official Tier 1 papers and independently solved — not taken from any candidate's recorded response.

Letter-Cluster: Find the Odd One Out (Q1–Q2)

Q1. Four letter-clusters are given, of which three are alike in some manner and one is different. Select the letter-cluster that is different.

1. FBXT  2. TPLH  3. CYUQ  4. NJFA

Show Answer

4. NJFA. In FBXT, TPLH, and CYUQ, each letter jumps forward by the same fixed gap of 22 positions (equivalent to −4 in the alphabet cycle). NJFA breaks this pattern on its final letter.

Q2. Four letter-clusters are given, of which three are alike in some manner and one is different. Select the letter-cluster that is different.

1. DFBA  2. RTPO  3. LNJI  4. FHDB

Show Answer

4. FHDB. DFBA, RTPO, and LNJI all follow the identical letter-position gap pattern (+2, +22, +25); FHDB breaks the pattern on its final letter.

Letter-Cluster Series (Q3)

Q3. Select the letter-cluster that can replace the question mark (?) in the following series: GCB, JHE, MMH, PRK, ?

1. RVM  2. TXO  3. SWN  4. SXM

Show Answer

3. SWN. Each of the three letter-positions increases by a fixed amount independently: the first letter by 3 each time, the second by 5, and the third by 3 — giving S, W, N.

Number Series (Q4–Q8)

Q4. Select the number that can replace the question mark (?) in the series: 37, 52, 74, 104, 143, ?

1. 168  2. 176  3. 202  4. 192

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4. 192. The differences between consecutive terms (15, 22, 30, 39) themselves increase by 1 more each time (7, 8, 9, then 10). Next difference = 39+10 = 49, so 143+49 = 192.

Q5. Select the number that can replace the question mark (?) in the series: 24, 48, 51, 204, 209, ?

1. 1047  2. 215  3. 1254  4. 416

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3. 1254. The pattern alternates ×2, +3, ×4, +5, ×6: 24×2=48, 48+3=51, 51×4=204, 204+5=209, 209×6=1254.

Q6. Which number will replace the question mark (?) in the series: 33, 80, 108, ?, 183, 230, 258

1. 160  2. 155  3. 143  4. 138

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2. 155. The differences alternate +47, +28 throughout: 33+47=80, 80+28=108, 108+47=155, 155+28=183, 183+47=230, 230+28=258.

Q7. Select the number that can replace the question mark (?) in the series: 2, 6, 9, 27, 30, 90, ?

1. 85  2. 88  3. 90  4. 93

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4. 93. The pattern alternates ×3, +3: 2×3=6, 6+3=9, 9×3=27, 27+3=30, 30×3=90, 90+3=93.

Q8. Which number will replace the question mark (?) in the series: 232, 221, 199, ?, 122, 67

1. 155  2. 165  3. 177  4. 166

Show Answer

1. 155. The differences between terms double each time (11, 22, 44, 88, 176): 232−11=221, 221−22=199, 199−44=155, 155−88=67. (176 leads to the final unseen term.)

How to Approach These Under Time Pressure

• For letter-cluster odd-one-out: convert letters to their alphabet positions (A=1...Z=26) and check the numerical gap between consecutive letters within each cluster — the odd one breaks a consistent gap pattern shared by the other three.
• For number series: always check the differences between consecutive terms first. If those differences aren't constant, check if the differences themselves follow a pattern (increasing by a fixed amount, alternating with multiplication, or doubling) — most series patterns reveal themselves at this second level.

Frequently Asked Questions

Q1. Why weren't more letter-cluster questions included?
We only publish questions we can independently verify with full confidence. Several extracted letter-cluster questions had patterns we couldn't confirm cleanly, so we excluded them rather than guess.

Q2. Are these the highest-frequency Reasoning topics in SSC CGL?
Based on our dataset analysis, Coded Language and Letter-cluster analogy are tied as the most frequent Reasoning sub-topics, with Series/number analogy close behind — see our Reasoning & Quant Practice Set for additional verified examples across other sub-topics.

Q3. Is there a faster way to spot number series patterns?
Practice recognizing the four most common pattern families first — constant difference, increasing difference, alternating operations, and doubling differences — since the vast majority of SSC CGL number series fall into one of these.

For more Reasoning and Quant practice, see our full Reasoning & Quant Practice Set.