SSC CGL Reasoning · Classification
Letter Gap Patterns
Letter clusters whose steps are not all the same: the gaps grow or shrink by a rule, or the letters move forward and back in turn. Write every gap and compare the whole list.
Why this matters
Thirty-nine questions in the bank, 14 from the 2023 shifts and 25 from the 2024 shifts, with 33 EASY and 6 MODERATE. The odd cluster usually differs in just one of its gaps, so the only safe method is to write every gap of every option and compare the lists side by side.
Concept 1 of 2: Gaps that grow or shrink by a rule
Definition
1. Turn every letter into its position (A1 to Z26, using EJOTY to count fast). 2. Under each cluster, write the gap from each letter to the next: +2, +3, +5. 3. Put the four gap lists side by side. Three are the same list; the fourth differs in one place. 4. A gap that runs past Z wraps round: carry on from A. From X (24) a step of +5 lands on 29, which is C (29 minus 26 = 3).
- Common gap lists: +1, +3, +5 (odd numbers); +2, +4, +6 (even numbers); +4, +3, +2 (falling by one); +2, +3, +5 (primes); +3, +5, +7.
- Fast route: compare the first gap of all four options, then the second, then the third. Stop as soon as one option stands apart; there is no need to finish the others. This is safe only when the other three agree on every gap you have checked so far.
Worked example
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 1 · Classification · Letter Gap Patterns
Checking only the first gap
Losing count when a step passes Z
Concept 2 of 2: Letters that move forward and back
Definition
1. Write each gap with its sign: + for forward along the alphabet, minus for back. 2. Compare the signed lists. KIM is minus 2, then +4; KMI would be +2, then minus 4, a different pattern. 3. Backward steps can wrap too: before A comes Z. Three steps back from C is Z. 4. In a four-letter cluster, the pattern may pair letters instead: the 2nd is the 1st plus 3, and the 4th is the 3rd minus 3. Check each pair on its own.
- Fast route: if the letters of one option all run in a single direction while the other three turn round, that option is usually the answer. Confirm it by writing the signed gaps once.
Worked example
Practice this conceptself-check · 4 quick reps
The same idea in a real exam question:
Example 2 · Classification · Letter Gap Patterns
Dropping the direction of a step
Wrapping the wrong way at the start of the alphabet
Summary — formulas & gotchas at a glance
A revision cheat-sheet for the formulas and gotchas above. Click any concept name to jump back to its full explanation.
Watch out for (4)
- Checking only the first gap→ Gaps that grow or shrink by a rule
- Losing count when a step passes Z→ Gaps that grow or shrink by a rule
- Dropping the direction of a step→ Letters that move forward and back
- Wrapping the wrong way at the start of the alphabet→ Letters that move forward and back
Test yourself on Classification
20 past SSC CGL questions from this chapter, timed at 12 minutes and marked the way the exam marks it. You see your score and every answer the moment you finish. Free to start.