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abacus; soroban
calculation (esp. of profit and loss); reckoning
そろばん教室に週二回通っている。
I go to abacus class twice a week.
そろばんが得意な人は暗算も速い。
People who are good at the abacus are also fast at mental math.
木製のそろばんは手触りがいい。
Wooden abacuses feel nice to the touch.