Continue a code whose two explicit rules alternate.
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34, 28, 22, 16, 10 … which carriage couples on the end?
This exercise practises follow alternating code rules alongside its own main skill, Number Series.
It covers most of this skill rather than all of it.
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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.
Two rules taking turns
Check the jump for each letter in turn - they are not all the same.
TAP → XHT, so OIL → ?
SMP
SPP
SQP
VMS
Answer: SPP
How you get there
TAP becomes XHT because the letters in odd positions move 4 places forward through the alphabet while the letters in even positions move 7 places forward through the alphabet, and the same rule turns OIL into SPP.
Why the other answers tempt
Using the first jump for every letter is the trap - the second jump is not the same one, and higher up it does not even run the same way.
If they are stuck, say this
Compare TAP with XHT one letter at a time: the odd letters move one distance and the even letters move another.
34, 28, 22, 16, 10 … which carriage couples on the end?
This engine’s own main skill is Number Series. It practises follow alternating code rules alongside it, and covers most of it rather than all.
Look at the couplings, not the carriages. The gaps between 34, 28, 22, 16, 10 are -6, -6, -6, -6 - and that is where the pattern lives: every coupling takes away 6. Carrying it on from 10 gives 4.
What to say if they get stuck
Press Roll - the ball hops between carriages and writes the gap into each coupling.
Every gap is the same size. Add it once more to the last carriage.
Where follow alternating code rules sits in the 11+
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 follow alternating code rules 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: continue a code whose two explicit rules alternate, and it stops where exactly two repeating rules.
Questions parents ask about follow alternating code rules
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.
Continue a code whose two explicit rules alternate. 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.
Using the first jump for every letter is the trap - the second jump is not the same one, and higher up it does not even run the same way. 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. Compare TAP with XHT one letter at a time: the odd letters move one distance and the even letters move another.
The skill map draws the line here: Exactly two repeating rules. 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 apply a letter shift and apply a number code rule. The alternating-rule task composes repeated single-rule applications. The alternating-rule task composes repeated single-rule applications. Each of those has its own page here.
Use Number Train, embedded on this page. It is the exercise the skill map attaches to follow alternating code rules, 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.
