What is the sum of the equal angles of the isosceles triangle RST ?

Question

(1) ∠R = 50°
(2) ∠S = 65°

itoyj · Answer

Diagram for question?

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Bunuel · Answer

You don't need a diagram to answer this question.

Kinshook · Answer

(1) ∠R = 50°
If ∠R = 50° is one of the equal angles 
The other angle = 80°
And sum of the equal angles = 100°
But if ∠R = 50° is NOT one of the equal angles
Equal angle = 65° 
And sum of the equal angles = 130°
NOT SUFFICIENT

(2) ∠S = 65°
If ∠R = 65° is one of the equal angles 
The other angle = 50°
And sum of the equal angles = 130°
But if ∠R = 65° is NOT one of the equal angles
Equal angle = 57.5° 
And sum of the equal angles = 115°
NOT SUFFICIENT

Combining (1) & (2)
(1) ∠R = 50°
(2) ∠S = 65°
If ∠R = 50° is one of the equal angles
100+65 = 165 = sum of 3 angles of triangle <>180 NOT POSSIBLE
If ∠R = 65° is one of the equal angles
130+50 = 180 = sum of 3 angles of triangle =180 POSSIBLE
Sum of equal angles = 130
SUFFICIENT.

IMO C

What is the sum of the equal angles of the isosceles triangle RST ?

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