Why are formal written algorithms important?
A formal written algorithm offers a reliable procedure which can be used to make any calculation efficiently. They are of less importance now that electronic calculators are widely available in everyday life. Until about 1970, ability to perform written algorithms accurately and efficiently was needed on a daily basis for employment in most businesses, including shops and banks. Computer and cash register calculation has replaced this, leaving mainly incidental computation that is often best done mentally. Subtraction and multiplication Of the four basic arithmetic operations (addition, subtraction, multiplication and division), this resource focusses on only two: subtraction and multiplication. The principles which are shown for these operations mostly also apply to the other two operations. In particular, there are strong commonalities between strategies for addition and subtraction (a pair of inverse operations) and multiplication and division (a pair of inverse operations). The res
