[GMAT math practice question]
The figure below shows parallelogram ABCD where ∠DAC = 60 and ∠DBC = 30. What is ∠BDC?
A. 15
B. 30
C. 45
D. 60
E. 75
The figure below shows parallelogram ABCD
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We have ∠OCB = ∠OAD = 60 since they are alternate interior angles. Since ∠OBC = 30°, we have ∠BOC = 180° – (30° + 60°) = 90°.
Then the two diagonals are perpendicular to each other, and quadrilateral ABCD is a rhombus.
Thus, triangle BCD is an isosceles with BC = DC.
Then we have ∠BDC = ∠DBC = 30°.
Therefore, B is the answer.
Answer: B
We have ∠OCB = ∠OAD = 60 since they are alternate interior angles. Since ∠OBC = 30°, we have ∠BOC = 180° – (30° + 60°) = 90°.
Then the two diagonals are perpendicular to each other, and quadrilateral ABCD is a rhombus.
Thus, triangle BCD is an isosceles with BC = DC.
Then we have ∠BDC = ∠DBC = 30°.
Therefore, B is the answer.
Answer: B
Math Revolution
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Score an excellent Q49-51 just like 70% of our students.
[Free] Full on-demand course (7 days) - 100 hours of video lessons, 490 lesson topics, and 2,000 questions.
[Course] Starting $79 for on-demand and $60 for tutoring per hour and $390 only for Live Online.
Email to : [email protected]