Sequences and Series


A. Solve the following questions related to a series.

  1. In an arithmetric progression, the 10th term is 21 while the 12nd term is 25. Find the common difference (d) and also the first two terms of the series.
  2. If the sum of the nth terms in an arithmetic progression is Sn = 3n + n2, find the 5th term of the series.



  1. The formula to find the nth term in an arithmetic progression is: an = a + (n-1)d
  2. The formula to find the sum of the nth terms in an arithmetic progression is Sn = n/2(2a + (n-1)d)


  1. d = 2, a1 = 3, a2 = 5
  2. a5 = 12

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