How to do running update (memory) tasks
Running updates: overwrite, don't accumulate
A value changes step by step — add, move, reset — and only the final state is asked. The skill is replacing what you hold at every step, leaving no residue of the old value.
Updated
A box holds 12 counters; put in 4, take out 7, put in 3 — how many now? Nothing is hidden in these items: every instruction is on screen. The load is the OVERWRITE. Each instruction must replace the value you hold, and the old value must be gone. Almost every miss in this family is a stale value that survived one step too long.
One number at a time — or two, labelled
Most chains track a single value through additions and subtractions — sometimes a doubling or halving. The harder ones run two counters or two jars in parallel and ask about them at the end — sometimes 'how much higher is the red counter than the blue one?'. Give each its own slot and say the label as you update: 'red 9 … blue 7 … red 12'.
Resets erase history
A mid-chain 'reset the total to 15' makes everything before it irrelevant. Do not average, adjust, or peek back — restart from 15 and continue.
Transfers touch both ends
'Move 3 from the red jar to the blue jar' is two updates, not one: red down 3 AND blue up 3. Updating only the jar you are later asked about is the transfer chain's signature miss.
Standing rules: check before you apply
Some chains open with a guard — 'ignore any instruction that would make the total negative', or a stated ceiling. Test each instruction against the guard BEFORE applying it: the instruction that trips the rule is skipped entirely, not clipped to fit. Forgetting the guard, and applying it to the wrong step, are both wrong options waiting for you.
The strategy
- Read any standing rule first; keep it in front of your mind.
- Update immediately, then let the old value go.
- On transfers, move the amount out AND in.
- At the end, answer what was asked: a final value, one jar, or the gap between two counters.
Common traps
- Adding a step onto a value you should have replaced.
- Carrying pre-reset history past a reset.
- Updating one side of a transfer.
- Applying an instruction the standing rule cancels.
- Reporting the wrong counter, or a counter's value instead of the difference asked for.
Speed · ~60s/item: Roughly 30–100 seconds by chain length. Update chains do appear on scored mock tests — the overwrite habit is score-relevant, not just practice hygiene.
Worked example
Hold ONE number, never a history: 16 replaces 12, then 9 replaces 16. Almost every miss in this family is a stale value that survived one step too long.
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