Answers

2014-02-12T15:50:47+05:30
Sn= n/2[2.a + (n-1)d].
here a= the 1st number.
       n= the number of terms(numbers).
       d= the difference of the 2nd & 1st term,3rd & 2nd term.........
       the difference is constant.

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2014-02-13T20:03:10+05:30
Sum of n no. of series is n(a1....an)/2 n=1,2,3......n
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