| That is addition, multiplication and the two inverse operations of subtraction and division. |
| In the twelfth century, there was a sudden multiplication of women's hospices, houses of reclusion, and beguinages of all sizes. |
| Basically they had to devise methods of multiplication and division which only involved addition. |
| People who needed to do many multiplications or divisions probably looked the answers up in a table, or hired someone who could. |
| They were all excited doing their addition, subtractions, multiplications and divisions, mentally and with abacus. |
| One could verify this by doing two different long multiplications and checking that they give the same answer. |
