MENTAL MODEL · M6073

Potato Paradox

StructureHigh supportLogic

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Version 1.0.0 · Updated 2026-07-30

CORE DEFINITION

You have 100 kg of potatoes with 99% water content. After dehydration, the water content drops to 98%. How much do the potatoes weigh now? Intuition says "a little less," but the answer is 50 kg (half the original). Because the dry matter increases from 1% to 2%, doubling its proportion, the total weight must halve.

SCAFFOLDING EFFECT

psychology

Reduce cognitive load

The failure of proportional intuition. When the base is extremely small (dry matter only 1%), a tiny proportional change (1% to 2%) implies a drastic change in total quantity. When dealing with extremely pure substances or high leverage, always use a calculator, not intuition.

anchor

Anchor fast decisions

The "Potato Paradox" is a counterintuitive weight problem: 100 kg of potatoes contain 99% water (i.e., 1 kg of dry matter); after drying to 98% water, the dry matter remains 1 kg but its proportion becomes 2%, so the total weight is only 50 kg. It exposes people's intuitive bias regarding "percentage changes" and "base quantities."

MINIMUM ACTION

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Practice this model in one real situation:

When encountering percentage changes, first identify the invariant (e.g., 1 kg of dry matter) and recalculate
distinguish between "relative change" and "absolute quantity"
stay alert to statements like "water content drops by only 1%"
verify with algebra rather than intuition
in metric management, be wary of the large consequences of seemingly small percentage changes.

Check to track your progress (stored locally)

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Source support: Explicit

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en.wikipedia.orghttps://en.wikipedia.org/wiki/Potato_paradoxZH · Explicit
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