1The elementary-school subject covering numbers and basic calculation, such as addition, subtraction, multiplication, and division.
息子は算数が得意で、計算問題をすぐに解いてしまう。
My son is good at arithmetic and solves calculation problems right away.
算数の宿題を手伝ってほしいと娘に頼まれた。
My daughter asked me to help her with her arithmetic homework.
小学一年生から算数の授業が始まる。
Arithmetic classes begin from the first year of elementary school.
2The act of working out an answer using numbers; can also refer to everyday, casual calculations.
割り勘の金額は簡単な算数で出せる。
You can work out the amount for splitting the bill with simple arithmetic.
頭の中で算数をして、おつりが正しいか確かめた。
I did the arithmetic in my head to check whether the change was correct.