arithmetic

Elementary school students must master mental arithmetic before they are allowed to use calculators in class.

(Chinese) 小学生在被允许在课堂上使用计算器之前，必须掌握心算。

The accountant noticed a simple error in arithmetic that resulted in a ten-thousand-dollar discrepancy.

(Chinese) 会计发现了一个简单的算术错误，导致了一万美元的差额。