The angles of a pentagon are x°, 2x°, (x + 60)°, (x + 10)°, (x -10)°. Find the value of x.

  • A 40
  • B 60
  • C 75
  • D 80
  • E 90
waec 1991mathematics

The correct answer is D. 80

Sum of ∠s in a pentagon = (n - 2)180 = 540°

x° + 2x° + x° + 60° + x° + 10° + x° - 10° = 540°

6x° + 60° = 540°; x = 80°

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