Geometry and TrigonometryEasy–MediumValue of x from an angle bisector
Geometry and Trigonometry practice question
Ray OC bisects angle AOB. If angle AOC measures (4x − 5)° and angle COB measures (2x + 25)°, what is the value of x?
Answer: 15
A bisector makes the two angles equal: 4x − 5 = 2x + 25, so x = 15.
Common wrong answers
- If you answered 10
- 10 solves 4x − 5 + 2x + 25 = 80, an invented total.
- If you answered 30
- 30 sets the two angles' sum to 180 without a reason.
- If you answered 55
- 55 is the measure of each angle, not x.
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