India capitalised on some sloppy fielding by South Africa to reach 523-6 on the third day of the second and final Test at the Eden Gardens in Kolkata on Tuesday.Earlier, at the lunch break, VVS Laxman (39) and skipper Mahendra Singh Dhoni (27) were at the crease for the hosts who must win the match to hold on to their number one spot in ICC rankings.Laxman's 39 came off 96 balls, while Dhoni, who had a few lucky escapes, took 45 balls to make his 27 runs.Earlier, night watchman Amit Mishra hit a quick-fire 38-ball 28 to put on a 48-run sixth wicket partnership with Laxman to help India extend the lead.Dropped on five by Jacques Kallis in the slip, Mishra took the attack to the Proteas camp. With Laxman displaying control at the one end, Mishra took on the pace of Steyn and the slow spin of Paul Harris to help India build on the lead.Hoping from some reverse swing from Kallis, Smith delayed taking the new ball by four overs as Mishra played with aggression.South Africa took the new ball in the 84th over but Mishra was undeterred as he scored almost run-a-ball.Mishra once again got a life when he was dropped by Smith (short extra-cover) while on 25.Mishra's innings was ended by pacer Dale Steyn in the very next over when he was caught by Kallis at the second slip.Laxman was slow in his approach and had luck on his side when he edged one to the left of an outstretched A B de Villiers who failed to pouch it.Dhoni joined Laxman in the middle for the sixth wicket as India continued scoring briskly taking a 100-run lead over South Africa in the 93rd over.India were almost 100 runs ahead of South Africa in terms of scoring rate. While South Africa were 296 in 85 overs, India were 380 for five at the same stage.Dhoni and Laxman milked the South African attack at ease with the skipper attacking Harris, charging one down over long-off for a six.The Dhoni-Laxman partnership remained undefeated on 47 stand at lunch.