South will now take on West Zone in the second semi-final slated on Tuesday.
Opting to bat the Nehru Stadium in Guwahati, South Zone posted a healthy total of 284 for five in 50 overs riding on Aparajith's 121. The India colts player played 129 balls and hit 10 fours and three sixes in his innings.
In reply, East managed to 273 for seven with skipper Wriddhiman Saha top-scoring with 77 and Ishank Jaggi managing to hit 55.
Having lost other opener Lokesh Rahul (0) in the very second over, Uthappa and No 3 batsman Aparajith added 95 runs for the second wicket before the former retired hurt.
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Skipper Dinesh Karthik (33) joined Aparajith and they added 59 runs for the third wicket.
The late flourish was provided by Kerala's one day captain Sachin Baby smashing an unbeaten 33 off 19 balls with five fours. The last five overs yielded 48 runs with India pacer Shami Ahmed giving away 60 runs in 11 overs.
Brief Scores: South Zone 284/5 (B Aparajith 121, R Uthappa 48, S Baby 33 no, Shami Ahmed 2/60)
East Zone 273/7 (Wriddhiman Saha 77, Ishank Jaggi 55, Abhimanyu Mithun 3/40).