mathematics tricks and fun

  Number NINE Number Nine is a peculiar and interesting number which is attributed different names in mathematics literature.Moreover it is a number which is equally valued  by all religions and  numerology,astrology, as well. 9 is natural number lying between numbers 8 and 10 It is the highest single  digit number in the base 10 system .This is a composite number its divisors  being 1 and 3 .  3 x 3  is 9 and so the third square num ber. It is the first  composite number and first composite odd number and also single digit  composite odd number. A polygon of 9 sides is called nonagon or  ennaegon. Group of nine of anything is called ennead. If any natural number is multiplied by 9, then its  digital sum is always nine.  This method of finding  digital sum and casting out nines is a quick way  of testing calculations of sums,differences,multiplications,divisions. This is known ever since 12th century.  Wh...