Which was the first film of Dharmendra-Hema Malini, in how many movies did both of them work together?

If reports are to be believed, Hema Malini-Dharmendra have worked together in about 31 films. Both of them did films like Dream Girl, Chacha Bhatija, Ali Baba Aur 40 Chor, Bagwat, Rajput, Rajtilak, Sholay, Sita Aur Geeta, Raja Jani, Jugnu, Dost, Charas and others. 20 out of his 31 films were hits.