MCQ
Find the sum of series 1+ 3+ 5+…………………………..+ 113.
  • A
    2556
  • B
    5248
  • C
    6589
  • D
    9874

Answer

  1. 2556

Solution:

1+ 3+ 5+…………………………..+ 113

= (1+ 2+ 3+……+ 113) – (23 + 4+ 6+ 8+ 103)

= (1+ 2+ 33+……113) – 23(1+ 23 + 3+ 4+ 53)

$\Big(\frac{11\times12}{2}\Big)^2-8\Big(\frac{5\times6}{2}\Big)^2$

$=66^2-8\times15^2$

$4356-1800=2556.$

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