Wednesday, June 6, 2012

Vedic mathematics technique to calculate the inverse of a prime number.


  • The solution consists of a digit part which is zero always.
  • The decimal part repeats after every (n – 1) digits.
  • The decimal part is calculated by multiplying (or dividing) each successive digit with a calculated fixed number.
  • The carry is added to (or subtracted from) the next successive digit. 

The fixed multiplicand is calculated as follows: 
  • Prime numbers ending with 1.
              E.g.:
                      Consider a number ab.
                      Then the fixed multiplicand is = ab - a
                          ·         1/11 = 11 - 1 = 10. 
                          ·         1/31 = 31 - 3  = 28. 
                          ·         1/71 = 71 - 7  = 64. 
                          ·         1/101 = 101 - 10  = 91.
                          ·         1/131 = 131 - 13  = 118.
                          ·         1/971 = 971 - 97  = 874.
      
    • Prime numbers ending with 7.
              E.g.:
                      Consider a number ab.
                      Then the fixed multiplicand is = (a × b) + 5.
                          ·         1/7 = (0 × 7) + 5. 
                          ·         1/17 = (1 × 7) + 5.
                          ·         1/977 = (97 × 7) + 5.

    • Prime numbers ending with 9.
              E.g.:
                      Consider a number ab.
                      Then the fixed multiplicand is = Ten’s digit  + 1
                          ·         1/19 = 1 + 1 = 2.
                          ·         1/29 = 2 + 1 = 3.
                          ·         1/1129 = 112 + 1 = 113. 

    • Prime numbers ending with 3.
              E.g.:
                      Consider a number ab.
                      Then the fixed multiplicand is = (a × b) + 1.
                          ·         1/13 (1 × 3) + 1.
                          ·         1/23 = (2 × 3) + 1.
                          ·         1/1123 = (122 × 3) + 1.


    Some solutions:
    1/7 = 0.142857…
    1/13 = 0.076923076923…
    1/17 = 0.0588235294117647…
    1/19 = 0.052631578947368421…
    1/23 = 0.0434782608695652173913…
    1/29 = 0.0344827586206896551724137931…