Question

Why did the narrator visit the village astrologer?what according to be astrologer was ranga's cause of worry?​

Answer 1

According to the astrologer the cause of Ranga’s worry was a girl. He meant to say that Ranga had been thinking about a girl. When asked what the name of the girl was, the astrologer after doing some fake calculations suggested the name of the girl had something found in the ocean such as ‘Kamla’, ‘Pachchi’, or ‘Ratna’. Actually it had all been planned beforehand by the narrator and the astrologer.

Answer 2

As you have said in the question it was the village area. people were illiterate there. it is shown from the fact when the villagers check the hands, legs, nose and eyes of ranga and even his sacred thread. For them education was the loss of one's identity.
So as related to the question villagers were superstitious. They believed in science but in science of astrology, as ranga was the native of the village he also respected village astrologer. So to free himself from his worry he moved on with the narrator. When astrologer said it was about a girl his belief in this faith went strong. that was the matter of faith that persauded narrator to go to the village astrologer