Amid highly volatile trading today, the BSE benchmark Sensex moved up for the third day in a row, gaining 100 points amid slight easing of the food inflation and a strong trend in global stock markets.The Bombay Stock Exchange 30-share index, Sensex, which had gained 352 points in the previous two sessions, advanced further by 100.54 points or 0.59 per cent to 17,165.54.In a similar fashion, the broad-based National Stock Exchange index Nifty moved between 5,169.25 and 5,098.25 before closing higher by 28.60 points at 5,153.25. Food inflation returned to single digit at 9.55 per cent for the week ended August 27, from 10.05 per cent in the previous week.