Digital PSAT Math Practice Question 289: Answer and Explanation

Question: 289

In the figure above, lines AB and XY are parallel, and line CD transverses them. Given that angle BCD is equal to 150 degrees, what is the measure of angle CDY in degrees?

Correct Answer: 30

Explanation:

30 Notice that angle CDY is an opposite interior angle of angle ACD; therefore, these two angles are congruent. Angle ACD is on the same line as angle BCD, so they must add up to 180°. Angle BCD is 150°, so angle ACD = 180° - 150° = 30°. Therefore, angle CDY is also 30°.