Carcass wrote:
![Image](https://gmatclub.com/forum/download/file.php?id=35639)
What is a + b + c + d?
A. 110
B. 120
C. 130
D. 150
E. Cannot be determined from the information above
I can see some triangles that include the necessary angles (a, b, c and d)
So, let's add some extra angles, x and y:
![Image](https://gmatclub.com/forum/download/file.php?mode=view&id=35650&sid=6f493b1f8f64bf0c9074b63c3a25a5fb)
Since x, 30 and y are on a line, we know that
x + y + 30 = 180
This means that
x + y = 150Now let's examine some hidden triangles. Here's one:
![Image](https://gmatclub.com/forum/download/file.php?mode=view&id=35649&sid=6f493b1f8f64bf0c9074b63c3a25a5fb)
Since angles in a triangle add to 180 degrees, we can write: a + c + x + 30 = 180
Subtract 30 from both sides to get:
a + c + x = 150Here's another hidden triangle
![Image](https://gmatclub.com/forum/download/file.php?mode=view&id=35651&sid=6f493b1f8f64bf0c9074b63c3a25a5fb)
Since angles in a triangle add to 180 degrees, we can write: b + d + y + 30 = 180
Subtract 30 from both sides to get:
b + d + y = 150We now have two equations:
a + c + x = 150b + d + y = 150ADD them to get: a + b + c + d + x + y = 300
Since
x + y = 150, we can write: a + b + c + d +
150 = 300
Subtract 150 from both sides to get: a + b + c + d = 150
Answer: D
Cheers,
Brent