Letter and Symbol Series

The three patterns to check first

Series problems look intimidating but reduce to three recurring patterns. Test them in order on every series.

• Constant gap: the difference between consecutive terms is fixed. Example 2, 4, 6, 8 — gap of 2; next term is 10.
• Increasing or geometric gap: the difference itself changes by a rule. Example 1, 2, 4, 7, 11 — gaps are 1, 2, 3, 4; next term is 16.
• Alternation: two interleaved series. Example 2, 10, 4, 20, 6, 30 — odd positions go 2, 4, 6 and even positions go 10, 20, 30.

Letter series: convert to numbers first

Map A=1, B=2, C=3 ... Z=26. The series A, C, E, G becomes 1, 3, 5, 7 — constant gap of 2; next is I (=9). For reverse alphabet items, use 27 minus position: Z=1, Y=2 from the back. The series Z, X, V, T becomes 1, 3, 5, 7 from the end; next is R.

Worked example with alternation

AZ, BY, CX, DW, ? Pattern: first letter advances A, B, C, D — next is E. Second letter retreats Z, Y, X, W — next is V. Answer: EV. Always split alternating series into two sub-series before guessing.

Symbol series

Symbol items typically rotate or reflect a shape. Track two attributes simultaneously — orientation and the number of marks (dots, lines). The trap is fixating on rotation while a dot is being added at every step.

Coding-decoding overlap

Many UHS items disguise series as coding. "If CAT = 24 and DOG = 26, then BAT = ?" Map letters to alphabet positions: C+A+T = 3+1+20 = 24. D+O+G = 4+15+7 = 26. So BAT = 2+1+20 = 23. The rule: sum of letter positions. Always sum and multiply first; products and sums cover most coding items.

If patterns fail: try squares, cubes, primes, Fibonacci

Series like 1, 4, 9, 16 are squares. 1, 8, 27, 64 are cubes. 2, 3, 5, 7, 11 are primes. 1, 1, 2, 3, 5, 8 is Fibonacci. After your first three checks, scan for these signatures.