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Sixteen Sutras exist, each finding uses in various parts of mathematics. A comment I made just now to a post on the Vedic Mathematics blog, however, has emphasised that you do not need to know all sixteen by name and all at once. You only need to know a couple at a time, to become familiar with them, and move on to others until you are familiar with the lot of them.
You can take your time learning VM, and as I commented:-
So it is okay to go slowly when approaching Vedic Mathematics, as a husband may approach his wife on their wedding night, knowing that Vedic Mathematics is a loving partner who will be with you, and faithful to you, forever.