# GRE Math : How to find an angle in an acute / obtuse triangle

## Example Questions

### Example Question #1 : How To Find An Angle In An Acute / Obtuse Triangle

The three angles in a triangle measure 3x, 4x + 10, and 8x + 20. What is x?

10

30

15

20

25

10

Explanation:

We know the angles in a triangle must add up to 180, so we can solve for x

3x + 4x + 10 + 8x + 20 = 180

15x + 30 = 180

15x = 150

x = 10

### Example Question #1 : How To Find An Angle In An Acute / Obtuse Triangle

In triangle ABC, AB=6, AC=3, and BC=4.

Quantity A                               Quantity B

angle C                   the sum of angle A and angle B

The relationship cannot be determined from the information given.

Quantity A is greater

Quantity A and B are equal

Quantity B is greater

Quantity A is greater

Explanation:

The given triangle is obtuse. Thus, angle  is greater than 90 degrees. A triangle has a sum of 180 degrees, so angle  + angle  + angle  = 180. Since angle C is greater than 90 then angle  + angle  must be less than 90 and it follows that Quantity A is greater.

### Example Question #74 : Geometry

In the figure above, what is the value of angle x?