Letter series and alphabet position

Learning outcome

You can continue a letter series by counting steps in the alphabet, including a pair of letters that move in opposite directions.

Concepts and reasons

Give every letter a place. A is 1, B is 2, and so on through Z at 26. A step of +2 from A lands on C. A step of -1 from Z lands on Y.

When the series is single letters, write the step between neighbours. A, C, F, J, O has steps +2, +3, +4, +5. The steps grow by 1, so the next step is +6. O is 15, and 15 + 6 is 21, which is U.

When each term is a pair, the two letters can have different rules. In AZ, BY, CX, DW the first letter goes A, B, C, D and the second goes Z, Y, X, W. The next pair is EV.

Worked examples

1. B, E, H, K, ? The step is +3. K is 11, and 11 + 3 is 14, which is N.
2. A, C, F, J, O, ? The next step is +6, so the letter is U.
3. AZ, BY, CX, DW, ? First letter +1 and second letter -1, so EV.

Common traps

Do not count the starting letter as a step. From A to C you pass B, but the step is +2, not +1. Z does not continue to A unless the question says the alphabet wraps. None of the series in this lesson wraps. Opposite letters are a different task. There, A pairs with Z because 1 + 26 = 27. That pairing is not the same as a moving series.

Practice questions

1. D, G, J, M, ?
2. Z, X, U, Q, ?
3. AB, CD, EF, GH, ?

Answers and explanations

1. P. The step is +3. M is 13, and 13 + 3 is 16, which is P.
2. L. The steps are -2, -3, -4. The next step is -5. Q is 17, and 17 - 5 is 12, which is L.
3. IJ. Each pair is the next two letters of the alphabet, in order. After GH comes IJ.

Analogy

The alphabet is a numbered street. A letter series is a walk along that street. Write how many doors you pass before you say which door comes next.

Quick reference

• A = 1 and Z = 26.
• Write the step, then continue the pattern in the steps.
• In a pair, each letter can have its own step.
• This lesson does not wrap from Z back to A.
• Opposite letters sum to 27. That is a code, not a moving series.