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Geometry and TrigonometryHardLargest angle from three expressions

Geometry and Trigonometry practice question

The angles of a triangle measure (2x + 10)°, (3x − 10)°, and x°. What is the measure, in degrees, of the largest angle?

Answer: 80

Sum to 180: 2x + 10 + 3x − 10 + x = 6x = 180, so x = 30. The angles are 70°, 80°, and 30°; the largest is 80°.

Common wrong answers

If you answered 30
30 is x, the smallest angle.
If you answered 70
70 is the middle angle (2 × 30 + 10).
If you answered 90
90 comes from 6x = 180 solved as x = 30 but then 3x = 90, forgetting the −10.

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