Yes,it is possible that even 10 parties can form a coalition.It can be better understood when the National Democratic Alliance was formed in May 1998 as grand coalition to contest the general elections.It was lead by Bharatiya Janata Party, including several regional parties, including the Samta Party,All India Anna Dravida Munnetra Kazhagam (AIADMK), Shiv Sena,where outside support was provided by the Telugu Desam Party (TDP).With this coalition NDA was able to win a majority in the elections of 1998