Since Roman times, Europeans had been struggling to do simple arithmetic with these
The Hindu or Arabic numerals made all kinds of calculation easier
In particular, Fibonacci showed how the new methods of calculation could be applied to commercial bookkeeping
to currency conversions and, crucially, to the computation of interest
Just imagine trying to work out percentages in Roman numerals
Fibonacci's Liber Abaci made it child's play
This was to be the application of mathematics to making money