"At present display is showing too much variations "

If I am not mistaken, 7109 is a dual slope ADC and you should get a very stable reading without any need for averaging.

Maybe the hardware setup ( signal conditioning and input stages ) are highly noisy. Unless you are sure that the hardware is NOT adding to the jitter, averaging will to an extent cure the symptom - but the disease will still go unchecked. And you will end up loosing accuracy.

Even when doing an average, try and do a moving average with about 10 samples. Try for searching with keywwords "Moving Average" and your query will be answered. If still you dont get it, mail me and I can forward a typical code.

Raghu