Find by how much percentage the average of first 10 odd numbers (starting from 1) is greater than the last term.

A)900/19 %


B)800/66 %


C)Cannot be determined

• Answer:
  First ten odd numbers form an arithmetic progression of the form
  1,3,5,7,9......
  here a = first term = 1
  d = common difference = 2
  Average of first n numbers = (2a + (n - 1)d)/2
  n th term of the AP = a + (n - 1)d
  Substituting a = 1, d = 2 and n = 10 in the above formulas
  average of first 10 numbers = 10
  10 th term of the AP = 19
  Therefore average of first 10 terms is 19 - 10 = 9 greater than
  the last term. Hence the average is greater than the sum by
  9/19 X 100 = 900/19 %
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