Banking is not, as they say, rocket science, but those who are afraid to do a little mental arithmetic will run into trouble.
www.npr.org The volume of the grain was carefully measured, based upon the mean width, length and height, and calculated by mental arithmetic, pen and paper, or slide rule.
en.wikipedia.org One criticism, for example, is that two relevant test features which an air traffic controller must possess are missing: left-right coordination and mental arithmetic.
en.wikipedia.org The presentation is immediately followed by the mental arithmetic component, during which the participant is asked to count backwards from 1,022 in steps of 13.
en.wikipedia.org Since the end of the 20th century, the term human computer has also been applied to individuals with prodigious powers of mental arithmetic, also known as mental calculators.
en.wikipedia.org