Letter Series

In a letter series question, a sequence of letters follows a pattern and you must identify the next term (or the missing term). Patterns are based on the positions of letters in the alphabet (A=1, B=2 … Z=26). Common patterns: every alternate letter (A, C, E, G — skip one each time), pairs moving forward (AB, CD, EF — consecutive pairs), fixed gap skip (+2: A, C, E; +3: A, D, G), or a combination of two interleaved series.

1. Write the alphabet with position numbers: A=1, B=2, C=3 … Z=26.
2. Find the gap between consecutive terms: C(3), F(6), I(9) — gap is +3 each time.
3. Check if the gap is constant (arithmetic series) or changing (+1, +2, +3 — increasing gap).
4. If the series looks like two interleaved patterns, separate the odd-position and even-position terms and analyse each separately.
5. Apply the confirmed rule to find the next term.

Example 1: A, C, E, G, ?

• Positions: 1, 3, 5, 7 — gap is +2 each time.
• Next position: 7 + 2 = 9 = I.
• Answer: I.

Example 2: AB, DE, GH, JK, ?

• First letter of each pair: A(1), D(4), G(7), J(10) — gap is +3.
• Second letter of each pair: B(2), E(5), H(8), K(11) — gap is +3.
• Next pair: M(13), N(14) = MN.
• Answer: MN.

• Confusing a +2 skip with a +3 skip — always count the positions precisely.
• In interleaved series, students analyse all terms together instead of separating odd and even positions, missing the two separate patterns.
• Series that reverse direction near Z (wrap to A) — if Z is position 26, the next +1 is A (position 1).

1. D, G, J, M, ? — what is the next letter?
2. AZ, BY, CX, DW, ? — what comes next?