Saha and Goswami put on an unbroken 150 for the opening wicket to score an easy win for Bengal with four overs to spare at the Eden Gardens.
Earlier, electing to bat, Assam put on 146 for 9.
Assam captain Arun Karthik scored a career-best 76 off 47 balls. The rest of Assam's line-up could not get going, the next best score by Swarupam Purkayastha's 15 off 20 balls, restricted in particular by medium-pacer Sayan Ghosh who took 3 for 30.
Summarised Scores:
Bengal 150 for no loss in 16 overs (Wriddhiman Saha 74 not out, Shreevats Goswami 71 not out) beat Assam 146/9 in 20 overs (Arun Karthik 76; Sayan Ghosh 3/30) by 10 wickets.
Tripura 192 all out in 19.5 overs (Udiyan Bose 74; Pratyush Singh 2/1) beat Jharkhand 168/6 in 20 overs (Shasheem Rathour 70; Joydeep Bhattacharjee 2/40) by 24 runs.