At stumps on the first day, Amit Sinha was batting on 20 while Tarjinder Singh was giving him company on 26, at the Nehru Stadium.
Das faced 186 balls and struck 15 boundaries during his stay at the crease.
Himachal Pradesh won the toss and elected to field.
Brief scores:
Assam 213 for four in 73 overs (P Das 90).