In the …Figure above, O is the center of a semicircle, and p

If we consider degree AOB=x, degree BOC=y, degree COD=z and degree DOE=w, there are 4 variables (x,y,z and w) and 2 equations (x+y+z+w=180 and x+y=85) in the original condition. In order to match the number of equations and the number of variables, there are 2 equations. Since the condition 1) and the condition 2) each has 1 equation, there is high chance that C is the correct answer.
Using the condition 1) and the condition 2) at the same time, we get y+z=100 and z+w=95. However, z+w=95 already appears in x+y=85. Hence, in overall, we lack 1 equation, which means the correct answer is E.



l For cases where we need 2 more equations, such as original conditions with “2 variables”, or “3 variables and 1 equation”, or “4 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 70% chance that C is the answer, while E has 25% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since C is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, D or E.

E You cannot determine the exact value.
Also i do not think that you can use similarity with the sectors of a circle, you will have to make some audacious assumptions to do so.

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