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% replaces any number of letters (la% - lake, lamp)_ replaces one letter (ca_ - car, cat)

Crossword clues for Calculator's ancestor 9 letters:

SLIDERULE: Calculator ancestor
SLIDERULE: Calculator's ancestor
ABACI: Calculators' ancestors
ABACUSES: Calculator ancestors
ABACUS: Calculator's ancestor
ABACUS: Ancestor of a calculator