Lines, Angles, and Triangles

SAT Math· difficulty 3/5

In an isosceles triangle, the vertex angle is 30°30° more than each base angle. What is the measure of the vertex angle?

  • A

    30°30°

  • B

    70°70°

  • C

    80°80°

    check_circle
  • D

    50°50°

Explanation

Let each base angle = bb. Then vertex = b+30b + 30. Sum: b+b+(b+30)=180b + b + (b+30) = 180, so 3b=1503b = 150, b=50b = 50. Vertex =80°= 80°.

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