Three angles of a quadrilateral are $80^{\circ}, 95^{\circ}$ and $115^{\circ}$. The fourth angle is:

Three angles of a quadrilateral are $80^{\circ}, 95^{\circ}$ and $115^{\circ}$. The fourth angle is:
  1. $60^{\circ}$
  2. $70^{\circ}$
  3. $80^{\circ}$
  4. $90^{\circ}$

Solution

Fourth angle $= 360 - (80+95+115) = 360 - 290 = 70^{\circ}$.

Asked in: IMO

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