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Initially one is to blow 30 blows Tashrat 3x, Tarat 3x and Tashat 3x for each and every group of individuals. If one is unable to do so then some Rabbanim permit one to blow Tashrat three times having in mind by the Shevarim Teruah that whichever is not correct is considered like the voice of an animal, not being done for the sake of a Mitzvah. See Chapter 11 Halacha 1 for the full details of this subject!
 As is the simple implication of the ruling of the Gemara Rosh Hashanah 34b, and Michaber:Admur in 590:1-2 that the 30 blows are Biblically required due to doubt as what consists of a Teruah, and so rules Ramban in Milchamos Hashem. However there are opinions in the Rishonim [Rosh:Chinuch:Ran] which bring Rav Haiy Gaon which rules that in truth only 9 blows are needed and there is no doubt at all, as all the sounds of the Teruah are valid.