Blue LED and archimedes’ screw: what they have in common

1. Step 1. Blue LED — is a kind of — LED. A blue LED.
2. Step 2. LED — is part of — Liquid-crystal display. LED backlighting.
3. Step 3. Liquid-crystal display — is part of — Electronic calculator. An LCD display.
4. Step 4. Electronic calculator — evolved from — Arithmometer. Electronics replaced mechanics.
5. Step 5. Arithmometer — has part — Crank. The handle for adding and subtracting.
6. Step 6. Crank — is part of — Archimedes’ screw. A handle or rotary drive.

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