Letter-number code questions are one of the highest-frequency Verbal Reasoning question types in GL papers. They test pattern recognition under tight timing.
What this question type tests
Code questions test the child's ability to map a sequence of letters onto a sequence of numbers (or another letter sequence) according to a rule, then apply the rule in reverse.
How it appears in real papers
In GL papers, codes typically appear as one of the early VR question types and account for around 8 to 12 marks out of a 50-question paper. Multiple sub-types exist: simple letter-shift codes, alphabet-position codes, and combined letter-number codes. Recognising the question type within five seconds is the marker of a confident candidate; recognising it after thirty seconds of re-reading typically means a lost mark on a tight paper.
The technique to learn
The technique is consistent across sub-types. Step one: write the alphabet down the side of your scrap paper with numbers 1 to 26 underneath. Step two: identify whether the code is a shift, a position, or a substitution. Step three: apply the rule.
For shift codes, count the gap once, then apply it consistently. The most common error is to count the gap wrong by one — counting "A to D" as 4 instead of 3. Practise counting gaps verbally to lock in the +1 / -1 distinction.
Worked example
Worked example: if "CAT" is coded as "FDW", what is "DOG"? Step one: alphabet 1-26 written out. Step two: C=3, A=1, T=20; F=6, D=4, W=23. The shift is +3 each letter. Step three: D+3=G, O+3=R, G+3=J. Answer: GRJ.
Common errors
Common error: applying the shift inconsistently across letters, especially when one of the letters wraps around the alphabet (Y+3 = B, not E). Wrap-around catches many otherwise-strong candidates.
Practice approach
Drill 10 code questions per session, three times a week. Mix sub-types within each session so the child practises identifying which technique to apply, not just executing one technique. Embedding the technique requires repeated exposure across different surface presentations — a child who has only seen one phrasing will be thrown by the next.