The offline interactive calculates invented examples. This page contains the same method, source numbers, worked examples, error test and limits. No device, account, sound, live price or purchase is needed.
Paper method: (1) State the original amount and unit. (2) Find the first dollar gap as original × first percent ÷ 100; add for a rise or subtract for a fall. (3) Name the new amount. (4) To return, divide the same dollar gap by the new amount, then multiply by 100 for the reverse percentage. (5) Test the mistaken repeated-first-percentage shortcut against the new amount. (6) Say that a word or image crop may hide one base; the values are fictional.
| Original | First step | New base | Correct return | Repeating first % instead |
|---|---|---|---|---|
$96 |
25% rise is $24 |
$120 |
$24÷$120×100=20% fall; $120−$24=$96 |
25% of $120 is $30; fall gives $90 |
$60 |
20% fall is $12 |
$48 |
$12÷$48×100=25% rise; $48+$12=$60 |
20% of $48 is $9.60; rise gives $57.60 |
Tactile route: Arrange three numbered raised-edge cards ORIGINAL, CHANGED and RETURN. Place a labelled dollar-gap token between each pair, and place a FIRST PERCENT and RETURN PERCENT token beside their own starting amount. Use Braille/large-text labels or speech for every token; texture alone is insufficient. Move the same gap amount, then calculate its percentage of the new base. The learner may direct a supporter to move pieces and state the conclusion.
Public sentence prompt: “In this invented model, the amount changed from [original] to [new] by [first percent] of [original]. Returning to [original] needs [reverse percent] of [new]. A same-number percentage in the opposite direction does not generally reverse it.” No real price trend, accessibility impact or future change is established.
Original resource rights: © NeuroForgeIO Pty Ltd 2026, SubjectNest, CC BY 4.0. Credit author, source, licence and changes. Inline interactive code is Apache-2.0.