そろばん· also ソロバン
abacus; soroban; calculation (esp. of profit and loss); reckoning
JLPT N2 Common word Also written 十露盤、珠盤
Noun
算盤そろばんとは日本にほんのアバカスのことだ。
A "soroban" is a type of Japanese abacus.
いや算盤そろばんやってるから暗算あんざん得意とくいなのかと思おもって。
No, I just thought that since you can use an abacus, you might be good at doing calculations in your head.