Method of mental calculation of 19x19
Provides a completely new mental method of multiplication from 11 to 19
This method can be understood in a few minutes and can be calculated on the fly.Provides a new mental calculation method of multiplication from 11 to 19.
Provides a completely new mental method of multiplication from 11 to 19
This method can be understood in a few minutes and can be calculated on the fly.Provides a new mental calculation method of multiplication from 11 to 19.
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