6 mistakes learners make with letter sequences, each one named and explained.
Deal with each position in the pair as its own separate sequence.
In a sequence where some pairs are reversed, the reversal is applied on the wrong step.
Two rules alternating means keeping track of which one is due, and that is one thing too many.
Question. AB, DC, EF, HG, ?
A common answer. JI
The answer. IJ
Why. The pairs alternate forwards and reversed, and after HG the next is a forwards pair.
Number the terms 1, 2, 3, 4. The odd ones follow one rule and the even ones the other.
One letter of the pair advances and the other is copied from the previous term.
Copying is what you do when a strand's rule has not been worked out.
Question. AZ, BY, CX, DW, ?
A common answer. EW
The answer. EV
Why. The W belonged to the previous pair, and the second strand moves every time.
Both letters change at every step unless the sequence shows otherwise.
The right rule is found and the letters land one place before or after the correct ones.
Counting through the alphabet in your head loses its place easily, especially past the middle.
Question. AB, CD, EF, GH, ?
A common answer. HI
The answer. IJ
Why. GH ends at H, so the next pair starts at the letter after H.
Write the alphabet along the top of the page once. Every letter question then becomes counting.
The second letter follows the pattern and the first one does not.
Two independent sequences are running at once and only one of them holds the attention.
Question. AZ, BY, CX, DW, ?
A common answer. FV
The answer. EV
Why. The first letters run A, B, C, D, so the next is E.
Write the two strands on separate lines. Then neither can be forgotten.
The pair given has a different internal gap from the pairs in the sequence.
The attention goes to how the pairs advance, and the gap inside each pair goes unchecked.
Question. AB, CD, EF, GH, ?
A common answer. IK
The answer. IJ
Why. Every pair in the sequence is two consecutive letters, so the answer must be too.
Check the shape of your answer against the shape of the given terms, not just its position.
The first letter follows the pattern and the second one does not.
The first strand is solved first and finishing it feels like finishing the question.
Question. AZ, BY, CX, DW, ?
A common answer. EU
The answer. EV
Why. The second letters go backwards one at a time: Z, Y, X, W, then V.
Check the size of the step in each strand against all the earlier terms.
WAJD spots these patterns in your child's answers and names the one behind their wrong answers, instead of just marking them wrong.