While Mary Kom outpunched Sweden's Juliana Soderstrom 3-0, Sarita also got the better of Belarus' Ala Yarshevich by a similar scoreline after dishing out thoroughly dominating performances.
Mary Kom set up a clash on Saturday with Germany's Azize Nimani, who stunned Asian Games bronze-medallist Nandintsetseg Myagmardulam of Mongolia.
Sarita, on the other hand, will square off against Mexico's Victoria Torres, who got a first-round bye.
In a clinical performance, Mary Kom outsmarted an opponent, who had the height and reach advantage.
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The 32-year-old Indian had worked hard on her reflexes ahead of the tournament and the efforts were there to be seen as she easily out-witted Soderstrom's attempts at attacking her.
The Asian Games gold-medallist used her left hooks to telling effect against Soderstrom, who failed miserably in capitalising on her reach.
While Mary Kom was all precision in her punches, especially the right jabs, Soderstrom's swings were mostly off-target.
Every attempt that the Swede made at attacking was blocked brilliantly by the swift-moving Manipuri.
Even though Soderstrom did manage to make an impression in the fourth round, she had already lost the larger battle to her more experienced Indian rival.
In the end, it was hardly a surprise that the judges unanimously picked Mary Kom as the winner.
Sarita was as aggressive, if not more, in her contest against Yarshevich. The Asian Games bronze-medallist took hardly a few seconds to get a measure of her rival and then went about decimating her with consummate ease.
The Indian, in fact, did not have to defend much against a rather timid Yarshevich.
The prestigious event -- the final qualifying event for women boxers in the three Olympic categories of 51kg, 60kg, and 75kg -- has 12 Rio tickets on offer.