How did roman architects and builders calculate ?

by lamar70

How could ancient Roman architects calculate things as precisely as the drop rate of the aqueducts or the pressure of water when building a canal, projects that today need a computer to be modelised and tested before even starting the building stage ? Did they do calculus and arithmetic...with the Roman numerals ??? Did they use an abacus like the Chinese ? Any insight is welcome!

Searocksandtrees