Manoj Tiwary's four wickets and Virat Kohli's unbeaten 128 helps visitors take an unassailable 3-1 lead.
India ride on all-round effort to clinch ODI series in Sri Lanka
Kohli's outstanding innings, including 12 fours and one six, was the fulcrum which enabled the tourists to power past Sri Lanka's total of 251 for eight.
India's number three did, however, have a worthy foil in Suresh Raina, who marched to an unbeaten 58 off 51 deliveries in a 144-run partnership with Kohli.
The form of the two batsmen in a strong batting order and Kohli's dogged determination for improvement meant it was always going to be difficult for Sri Lanka even though India lost their fourth wicket at the score of 109.
"It's been going well for me, just trying to keep it simple," Kohli said at the post-match briefing.
"I got set and got out in the last match, I thought about it. I didn't have the strike rate to set up a platform for the side."
He did yesterday and as Mahela Jayawardene conceded: "To control that [batting] line-up you need to pick up wickets; dropping catches doesn't help.
"The wicket was a touch slow. We didn't bat well either, we were 30-40 runs short. When you set a target like that, you have to set attacking fields. If you get through that initial period, it becomes easy for them."
It was not all plain sailing for the visitors, though, as they lost a wicket without a run on the board. Gautam Gambhir, who made a magnificent 102 in the third one-day international, was dismissed after just five deliveries when Lasith Malinga's renowned swinging yorker unhinged his middle stump.
Virender Sehwag and Kohli soon had a calming effect on the Indian top order with a valuable 48-run alliance. Sehwag had ghosted menacingly on to 34 before his attempted flick to legside off Angelo Mathews was skilfully caught by the substitute fielder Sachithra Senanayake.
Much was expected of Rohit Sharma, but he again disappointed with the bat when adjudged lbw off a cute Nuwan Pradeep delivery for just four. Manoj Tiwary was then trapped in front by Jeevan Mendis for 21, before Raina and Kohli went about their business with ruthless efficiency.
Having won the toss, Sri Lanka will no doubt reflect on what could have been after having made a deeply promising start with an 86-run stand between the openers Upul Tharanga (51) and Tillakaratne Dilshan.
Dilshan reached 42 before his time came to an end when Ashok Dinda's short delivery lured him into a pull shot which was top-edged to MS Dhoni, the wicketkeeper.
Tharanga reached his half-century shortly afterwards before being dismissed by Ravi Ashwin one run later.
Lahiru Thirimanne also weighed in with a handy 47, while Rangana Herath (17 not out) and Malinga (15 not out) added a zesty flurry of late runs.
Sadly for the home side, it was not enough as part-time bowler Tiwary chipped away with four wickets for 61 runs, drawing praise from his captain Dhoni.
"The part-timers bowled really well. They bowled to their field. What also matters is the variations you have, Manoj was the away going spinner for us. If we don't get a perfect all-rounder, we are comfortable playing seven batsmen."
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