Result register and centrifugal pump: what they have in common

1. Step 1. Result register — is part of — Arithmometer. The carriage with the result.
2. Step 2. Arithmometer — has part — Crank. The handle for adding and subtracting.
3. Step 3. Crank — is part of — Mangle. A handle.
4. Step 4. Mangle — evolved into — Washing machine. Early machines had rollers for wringing.
5. Step 5. Washing machine — has part — Centrifugal pump. A drain pump.

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