Tripura, who scored a mammoth 549 in the first innings, logged three points by virtue of their first innings lead to jump to third place with nine points ahead of Himachal Pradesh, who had to settle for a point.
Resuming on 19 for one in their second innings while following-on, 20-year-old Bains followed up his first innings half-century with a solid century from 182 balls (13×4).
The wicketkeeper-batsman stood in three fifty-plus partnerships in the middle en route to his fourth first-class century, even as Tripura left arm spinner Gurwinder Singh (4/96) claimed regular breakthroughs.
Bains knock ensured that they overcame the deficit but soon he was trapped lbw by Singh ahead of the tea break and Tripura were in a sight of win. But an unbroken 107-run partnership between Gangta (64 not out) and skipper Rishi Dhawan (54 from as many balls) forced a draw.
Himachal Pradesh: 311 & 349 for 5 in 80 overs (Ankush Bains 113, Nikhil Gangta 64 not out, Rishi Dhawan 54 not out, Prashant Chopra 51; Gurwinder Singh 4/96).
Points: Tripura 3, Himachal Pradesh 1.