Digital PSAT Math Practice Question 148: Answer and Explanation

Question: 148

A four-sided figure has three interior angles of the same measure and the other interior angle measuring 120 degrees. What is the measure of the smallest interior angle in the figure?

• A. 40 degrees
• B. 50 degrees
• C. 65 degrees
• D. 80 degrees

Correct Answer: D

Explanation:

(D) The internal angles of a quadrilateral add up to 360 degrees. Since one angle is 120 degrees, the other angles will add up to 360 - 120 = 240 degrees. Since the other angles are all congruent, divide 240 by 3 to get 80 degrees as the measure of the other angles. 80 degrees therefore is the measure of the smallest interior angle.