The modern system of numbering, in which the digits depend on their position for their value, has been wrongly designated as Arabic numerical notation. The method is, in fact, of Indian origin. By the 9th century, much of the Hindu science was available in Arabic, thanks in good measure to frequent visits by Arab merchants to India. Sometime around 830 AD, the Persian mathematician, Al-Kwarizimi, in his Arithmetic used the Hindu method of notation. Since he had gathered information from the Arabs, he mentioned the numerals as Arabic system of numbering. Gradually, the methud spread to Europe, taking the place of the Roman system which was useless for calculations. Imagine trying to multiply VII by XL and eventually you hope getting CCLXXX! By using Indian method, the multiplication can be done instantly. It’s simply 7 times 40. Modern mathematics is indebted to the Indians who invented decimal system about 2,000 years ago!

Additional reading:

Arabic numerals (Wikipedia)