At the break, Rahul was batting on 106 (256 balls, 12x4, 1x6) with skipper Virat Kohli (67 batting, 121 balls, 11x4) giving him company as the two batsmen put on 137 unbeaten runs for the third wicket.
India still trail by 338 runs after Australia had declared their innings closed at 572 for 7 in their first innings.
The 22-year-old Rahul, playing in only his second Test match, was dropped by Australian captain Steven Smith when on 46 in the morning session at the SCG.
India had only scored 51 runs in two hours' play before lunch, but they made amends as 45 runs came in the first hour and then another 67 runs in the next hour until tea as normalcy was restored.
Much of this could be attributed to Kohli's batting, as he raced along to yet another half-century in this series, following his three hundreds already. He got there in the 80th over of the innings, off 108 balls.
Kohli was batting on 59 then and happily went to the break given this life. Perhaps his joy was emboldened with the fact that the young opener Rahul overcame his horrific debut Test in Melbourne to achieve a milestone. Rahul got there in 85th over, the last before tea, off 253 balls.
