Put into bat, Rahane struck 111 from 108 balls en route to his second ODI century while Dhawan returned to form with a 107-ball 113 as India posted an imposing 363 for five. Teams:
It was Dhawan's first hundred since his 119 against West Indies in Kanpur in November last year and sixth overall as the two Indian openers capitalising on their respective dropped chances by veteran wicketkeeper Kumar Sangakkara.
In their huge partnership, Rahane and Dhawan plundered 32 boundaries, including five sixes, between them.
Suresh Raina, appearing in his 200th ODI, also did his bit by striking a quick-fire 52 off 34 balls as it was one-way traffic for India.
India continued to dominate the proceedings as bowlers took the baton from the batsmen. They called the shots, bundling out the 'under-prepared' visitors for a mere 194 in 39.1 overs.
The pacers, led by Ishant Sharma, and spinners bowled with authority, never allowing the Sri Lankans to build partnerships or score freely.
Delhi lad Ishant made an impressive comeback to the One-day side after a gap of one year as he accounted for four batsmen and conceded just 34 runs in his 8 overs.
He had both Kumar Sangakkara (13) and Ashan Priyanjan (12) caught behind and later added two lower-order batsmen to his kitty.
Seasoned campaigner Mahela Jaywardene put up some resistance with a fiery 43 off 36 balls for the Lankans but other batsmen failed to put up fight.
Skipper Angelo Mathews (23) tried to dig in but half of his side was back in pavilion by the half-way mark in their chase at a score of 126 and he too could not survive for long.
India received an injury scare as paceman Varun Aaron left the field grimacing in pain after bowling the first ball of the 13th over. Skipper Virat Kohli completed the over.
Aaron, who clocked 152kph in the first over, chatted with Kohli as physio was called before the pacer was taken off.
The two teams will now travel to Ahmedabad for the second match on Thursday.
India: S Dhawan, A Rahane, V Kohli (capt), A Rayudu, S Raina, W Saha, A Patel, R Ashwin, U Yadav, V Aaron, I Sharma.
Sri Lanka: U Tharanga, T Dilshan, K Sangakkara, M Jayawardene, A Mathews (capt), A Priyanjan, T Perera, S Prasanna, S Randiv, D Prasad, L Gamage.
Put into bat, Rahane struck 111 from 108 balls en route to his second ODI century while Dhawan returned to form with a 107-ball 113 as India posted an imposing 363 for five.