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1. 1+3+6+ ... +21+24 = কত?

  • A. 218
  • B. 218
  • C. 218
  • D. 218

Answer: Option D

Explanation:

1 + 3 + 6+ … + 21 + 24

= 1+3×(1+2+…7+8)

= 1+3×{8×(8+1)}/2

= 1+3×36

= 1+108

= 109

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