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After skipper Virat Kohli opted to bowl on winning the toss, Indian spinners Ravindra Jadeja, R Aswhin and Amit Mishra shared eight wickets between them to skittle out Afghanistan for 159 in 45.2 overs.
The Indians chased down the target in 32.2 overs to clinch the bonus point but it was a case of too little too late after defeats against Sri Lanka and Pakistan poured cold water on their final hopes.
Ajinkya Rahane (56), after being promoted to open, and Shikhar Dhawan (60) set up the chase for India with a 121-run opening wicket partnership.
Earlier, Mohammed Shami provided India the first breakthrough by dismissing Nawroj Mangal (5) and thereafter it was a one-sided contest as Jadeja ripped through the inexperienced batting to finish with figures of 4/30.
Ashwin (3/31) also chipped in to fox the Afghans, who will go out with their heads held high after beating Bangladesh during the course of their campaign.
Afghanistan's innings centered around No 8 batsman Samiullah Shenwari, who scored a sensible 50 from 73 balls to give their total a semblance of respectability after a top-order collapse left them reeling at 95/7.
Having played safe by not fiddling with the playing XI even in a dead rubber against Afghanistan, India sent Rahane in the opening slot, a move that clicked as he and Dhawan put on a century partnership.
The duo played mostly in ground strokes and Rahane impressed up the order with his composed batting. The youngster, who usually bats at number four, settled in quickly and rotated the strike to take pressure off Dhawan, a tentative-starter who got a reprieve on 28.