One of the oldest calculating device was ______.
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arithometer
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ready reckoner
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abacus
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None of these
C
Correct answer
Explanation
The abacus is one of the oldest known calculating devices, dating back to ancient civilizations around 3000 BCE. It consists of beads on rods used for arithmetic calculations. The arithmometer came much later (19th century), and 'ready reckoner' refers to printed calculation tables, not a physical device.