Apply one arithmetic mapping to a letter or number code.
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Practise it now
Work out which two gears turn these numbers into those numbers.
This exercise practises apply a number code rule alongside its own main skill, Function Machines & Inverse.
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A worked example
One question of the kind this skill is tested with, worked all the way through: the reasoning, and what the wrong answers are there to catch.
Finding what one letter is worth
In a code, EAR is written 6 2 19. Using the same rule, how is NEW written?
Work one coded word out letter by letter and see why the rule has to be stated before it is used.
13 4 22
14 5 23
16 7 25
15 6 24
Answer: 15 6 24
How you get there
Each letter is worth its place in the alphabet, counting forwards from A, so A is 1, B is 2 and Z is 26 and then adding 1. That is what turns EAR into 6 2 19: E is 6, A is 2, R is 19. Doing the same to NEW gives 15 6 24. "13 4 22" is what you get if you work the rule out from one letter and then apply it slightly differently, which is why the rule is worth writing down as a sentence before you use it on the second word.
Why the other answers tempt
Getting the first letter right does not prove the rule: check it against a second letter of the same word before you trust it.
If they are stuck, say this
Write the alphabet out with 1 to 26 under it, then compare the first letter of the coded word with its number to work out what has been done to it.
Work out which two gears turn these numbers into those numbers.
This engine’s own main skill is Function Machines & Inverse. It practises apply a number code rule alongside it.
A function machine does the same thing to every number that enters it. You found the rule backwards - from the outputs - which is inverse thinking. And the order of the gears is part of the rule: ×3 then +1 turns 2 into 7, while +1 then ×3 turns the same 2 into 9. Same gears, different machine.
Step 1. Deduce the gears. Drag gears into the machine so every ticket comes out right.
Step 2. Run it. New number going in. Predict the output BEFORE you pull the lever.
What to say if they get stuck
Look at 2 → 7 and 4 → 13. When the input goes up by 2, the output jumps by 6. What multiplies by 3?
Try ×3 first: 2 becomes 6, but the ticket says 7. What tiny gear finishes the job?
The order of the gears changes the answer. ×3 then +1 gives 7; +1 then ×3 gives 9.
The 11+ does not test these skills in isolation, and practising one in the wrong order wastes the practice. These are the skills the curriculum map connects this one to.
The alternating-rule task composes repeated single-rule applications.
How apply a number code rule differs from the skills beside it
The same exercise practises several skills, and telling them apart is often the difficulty rather than the exercise itself. On this page the skill is: apply one arithmetic mapping to a letter or number code, and it stops where one invariant rule only.
Questions parents ask about apply a number code rule
Answered from what the skill map records about this skill, not from a template. Every answer here is on the page, and the same questions are the page's FAQ structured data.
Apply one arithmetic mapping to a letter or number code. It is one of 26 named verbal reasoning skills in the 11+, in the code strand, and this page carries 1 interactive exercise that practises it.
Getting the first letter right does not prove the rule: check it against a second letter of the same word before you trust it. The wrong answers on this skill are built out of that, not out of random numbers, so it is worth naming out loud before your child meets it under time pressure.
Point at the next move rather than explaining the whole rule. Write the alphabet out with 1 to 26 under it, then compare the first letter of the coded word with its number to work out what has been done to it.
The skill map draws the line here: One invariant rule only. A question past that line is testing a different named verbal reasoning skill, which is worth knowing before you spend a week practising the wrong one.
The skill map connects it to follow alternating code rules. The alternating-rule task composes repeated single-rule applications. That skill has its own page here.
Use Function Machine, embedded on this page. It is the exercise the skill map attaches to apply a number code rule, it runs in the browser with no account to make, nothing is scored, and nothing a child does here is recorded or sent anywhere. It also has its own link, so you can send it to a child without sending them anywhere else first.
Verbal reasoning is a set of question types, not a subject to revise
A free diagnostic works out which of the codes, analogies, word puzzles and logic types are already secure, and which are not.
