How did Romans do the calculations?

Read the text and answer the following questions:
1) What numerals are used in mathematics? 2) Are Roman numerals often used in mathematics? Why? 3) What instrument was used by the Romans for performing calculations? 4) What operations are difficult to perform with Roman numerals? 5) In what spheres of life are Roman numerals still used?
           How did Romans do the calculatons necessary for construction and other purposes using Roman numerals? 
     Our idea of a good time does not include trying to do long division with Roman numerals. Can you imagine dividing CXVII by IX and carrying down numbers that look more like a cryptogram than an arithmetic problem? The Romans were saved that torture. The Romans relied on the Chinese abacus, with pebbles as counters, to peform their calculations. In fact, Barry Fells, of the Epigraphic Society, informs us that these mathematical operations were performed in Roman times by persons called "calculatores". They were so named because they used calcule (Latin for pebbles) to add, subtract, multiply and divide.