OG13 DS 149



In the figure above, what is the value of x + y
1.x = 70
2.∆ABC and ∆ADC are both isosceles triangles

Important point: For geometry DS questions, we are typically checking to see whether the statements "lock" a particular angle or length into having just one value.

This concept is discussed in much greater detail in our free video: https://www.gmatprepnow.com/module/gmat- ... cy?id=1103

Statement 1 locks angle x by forcing it to have just one value (however it does not lock angle y).

Statement 2 forces the two triangles to be isosceles but the statement does not force the angles to have any particular values.

When we combine the statements, we should try to mentally grab points and try to move them (and still conform to the rules dictated by the statements). In this question, we can "grab" point D and pull it up or down, while still maintaining a 70-degree angle for x AND keeping the triangles as isosceles triangles. As we move point D up and down, angle y changes. So, there's now way that x+y can have a fixed value.

This means the answer is E

Cheers,
Brent

double post