If three angles of a quadrilateral are $75^{\circ}, 90^{\circ}$ and $75^{\circ}$, the fourth angle is:

If three angles of a quadrilateral are $75^{\circ}, 90^{\circ}$ and $75^{\circ}$, the fourth angle is:
  1. $100^{\circ}$
  2. $110^{\circ}$
  3. $120^{\circ}$
  4. $140^{\circ}$

Solution

Fourth angle $= 360 - (75+90+75) = 360 - 240 = 120^{\circ}$.

Asked in: IMO

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