Nine
festival nights for the goddesses of wealth (Lakshmi), Learning
(Saraswathi) and Courage/Bravery (Durga). The ‘victorious
tenth’ (Vijayadasami) day is considered auspicious for beginning
any activity, such as Learning, Business, etc.
http://www.chennaionline.com/specials/
navarathiri2002/navarathiri.asp