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The nine interior angles of a nine-sided polygon are in AP. The smallest is 120 degrees and each next angle is 5 degrees larger.
What is the total of all nine angles?

Class 10Sum of n Terms of an APAlgebra — Sequences
  • A1080 degrees
  • B1620 degrees
  • C2520 degrees
  • D1260 degrees

Step-by-Step Solution

[240 + 8(5)] = degrees. This agrees with the polygon rule , so the given data is consistent. The value 1080 is , one side too few, and 1620 is . 2520 is the AP sum with the factor left out.
Answer: D) 1260 degrees

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