The correct answer is Aryabhatta. AryabhattaAryabhatta was the first well-known exponent of Algebra among Indian Mathematicians. He calculated the value of pi to four decimal digits. He is also a well-known Indian astronomer. He is the author of ‚¬ËœAryabhatiya‚¬„¢, writing based on astronomy. He formulated the diameter value of the Earth as 12,742 km. Important Points Achievements of AryabhattaHe stated that 'Earth is a sphere that rotates on its axis'. He calculated the hours in a day as 23 hours, 56 minutes and 4. 1 seconds. He explained about the lunar eclipse. He found the distance between the Earth and Moon. He created a phonemic number notation system. Additional InformationVarahamihraHe is also known as Mihira. He was an ancient Indian astrologer, astronomer, and polymath. He is one of the 'Nine Jewels' of the court of ruler 'Yashodharman Vikramaditya'. His famous works were the 'Brihat Samhita', an encyclopedia on architecture. BrahmaguptaHe was an Indian mathematician and astronomer. He is the author of works on mathematics and astronomy known as the Brahmasphutasiddhanta and the Khandakhadyaka, respectively. He was the first to give rules to compute zero. BhaskaraHe was a seventh-century mathematician and astronomer. He was the first to write numbers in the Hindu decimal system. Indian Space Research Organisation (ISRO) launched Bhaskara I to honour him. He wrote a book named 'Mahabhaskariya' dealing with mathematical astronomy.