Letter Series Questions for SSC CHSL

Alphabet Position — The Foundation

Every Letter Series question depends on knowing where each letter sits in the alphabet. A=1, B=2, C=3 ... Z=26. You must recall positions instantly. Also memorise the reverse: Z=1, Y=2, X=3 ... A=26 (used in mirror/opposite questions). The midpoint is between M(13) and N(14).

• A to M = 1 to 13 (first half), N to Z = 14 to 26 (second half)
• Opposite pairs: A-Z, B-Y, C-X, D-W, E-V, F-U, G-T, H-S, I-R, J-Q, K-P, L-O, M-N
• Memorise positions of key letters: E=5, J=10, O=15, T=20, Y=25
• Every 5th letter trick: E, J, O, T, Y — positions 5, 10, 15, 20, 25
• Use the formula: position from end = 27 minus position from start

Types of Letter Series Patterns

SSC CHSL tests a fixed set of pattern types. Once you identify which pattern is running, the answer is automatic. The most common patterns are: fixed step (add same number each time), alternating step (add different numbers alternately), skip pattern (every nth letter), reverse series (going backwards), and group/block patterns where 2-3 letters form one unit.

• Fixed Step: A, C, E, G — each letter jumps +2 positions
• Alternating Step: A, B, D, E, G, H — pattern is +1, +2, +1, +2
• Reverse/Decreasing: Z, X, V, T — each letter jumps -2 positions
• Group Pattern: ABC, DEF, GHI — each group is the next 3 consecutive letters
• Two/Three Interlaced Series: A, D, B, E, C, F — two series running alternately (A,B,C and D,E,F)
• Repeated Pattern: AABBAABB — identify the repeating block

Group and Block Letter Series

Some questions show groups of 2 or 3 letters as one term. You must spot the pattern within each group AND across groups. Check: do the first letters of each group form a series? Do the last letters? Is there a relationship between letters inside one group? This type looks harder but breaks into simple sub-series once you split and analyse.

• Always check first-letter pattern, middle-letter pattern, last-letter pattern separately
• Common trick: first letter +1, last letter -1 across groups
• Watch for mirror pairs inside a group: like AF (A=1, F=6, sum=7) or BG (2+5=7)
• Sometimes internal gap within a group stays constant: like AC (gap 2), BD (gap 2), CE (gap 2)

Continuous Letter String (Fill in the Blanks)

A common SSC CHSL variant gives a string like: a_bc_a_bca_b_a and asks you to fill blanks to make a repeating pattern. The trick is to find the repeating unit first. Count total positions, guess a short repeating block (usually 3-5 letters long), and verify it fits all given letters.

• Identify total length of the string including blanks
• Try repeating block of 3, 4, or 5 letters — see which one fits all given letters
• Most SSC patterns repeat a 4 or 5 letter block
• Once you find the block, blanks fill automatically
• Write out the repeating sequence aligned with the given string to double-check

• Confusing position from start with position from end — always clarify which direction before solving
• Missing an interlaced (two alternating) series — if single-step pattern fails, immediately try every-other-term approach
• Assuming all series go forward — many SSC questions use a decreasing/reverse series, especially Z to A direction
• In group series, looking at the whole group instead of splitting into sub-series for each position — this wastes time and causes errors
• Miscounting letter positions under exam pressure — practise E=5, J=10, O=15, T=20, Y=25 as anchor points to count faster

• EJOTY trick: E=5, J=10, O=15, T=20, Y=25 — memorise this word EJOTY and you can reach any letter position in under 3 steps
• Opposite pairs rhyme trick: A-Z, B-Y, C-X (think ABC backwards is ZYX) — just pair them from both ends of alphabet
• Two series hiding in one — think of odd positions as one train, even positions as a second train running on parallel tracks
• For group series, read it like a table — rows are groups, columns are positions 1, 2, 3 — find the column patterns separately

• SSC CHSL typically asks 2-3 Letter Series questions — they appear in the first half of Reasoning and are considered easy-scoring, so target all of them
• Most questions are solvable in 20-40 seconds if you spot the pattern in the first 3 terms — if you cannot see it in 45 seconds, skip and return
• The continuous string fill-in-the-blank type is popular in recent CHSL papers — practise at least 10 of these before exam
• Difficulty is usually easy to medium — no tricks like complex coding, just clean arithmetic on letter positions
• Write letter positions on your rough sheet quickly using EJOTY anchors rather than counting from A every time — this alone saves 10-15 seconds per question