Q21 / 57 · KVPY 2019 (SA) · Mathematics

Let an,n≥1, be an arithmetic progression with first term 2 and common difference 4 . Let Mn be the average of the first n terms. Then the sum ∑n=110Mn is

  • Correct answer
    A
    110
  • B
    335
  • C
    770
  • D
    1100

Solution

 The sum of first n,n≥1 terms of arithmetic progression with first term 2 and common difference 4, is
Sn=n2[4+(n-1)4]=2n2
So, the average of the first n terms

Mn=Snn=2n

 Now, ∑n=110 Mn=2∑n=110 n

=2×10×112=110

Hence, the correct answer is option: 'A'.

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