Question counte

4.1 Lines, Angles, and Triangles - Angle relationships (parallel lines)
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  • Counterclockwise from top right, the lines are labeled s, r, q, and t.
  • Line s intersects line r above line q.
  • Line s and line r each intersect line q and line t.
  • At the intersection of line s and line r, 1 angle is labeled counterclockwise from top as follows:
    • Top: a/li>
  • At the intersection of line s and line q, 1 angle is labeled counterclockwise from top-left as follows:
    • Top left: b/li>
  • At the intersection of line r and line t:
    • The line segment divides the bottom-left angle into two equal angles, each labeled w/li>
  • A note indies the figure is not drawn to scale.

In the figure, parallel lines q and t are intersected by lines r and s . If a = 43 and b = 122 , what is the value of w ?

Enter your answer:

Counterclockwise from top right, the lines are labeled s, r, q, and t. Line s intersects

Hard-difficulty · SAT Math · Lines, Angles, and Triangles — Angle relationships (parallel lines). Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

The correct answer is 101 2 . In the figure, lines q , r , and s form a triangle. One interior angle of this triangle is vertical to the angle marked a°; therefore, the interior angle also has measure a°. It's given that a = 43 . Therefore, the interior angle of the triangle has measure 43°. A second interior angle of the triangle forms a straight line, q , with the angle marked b°. Therefore, the sum of the measures of these two angles is 180°. It's given that b = 122 . Therefore, the angle marked b° has measure 122° and the second interior angle of the triangle has measure 180-122°, or 58°. The sum of the interior angles of a triangle is 180°. Therefore, the measure of the third interior angle of the triangle is 180-43-58°, or 79°. It's given that parallel lines q and t are intersected by line r . It follows that the triangle's interior angle with measure 79° is congruent to the same side interior angle between lines q and t formed by lines t and r . Since this angle is supplementary to the two angles marked w°, the sum of 79°w°, and w° is 180°. It follows that 79+w+w=180, or 79+2w=180. Subtracting 79 from both sides of this equation yields 2w=101. Dividing both sides of this equation by 2 yields w = 101 2 . Note that 101/2 and 50.5 are examples of ways to enter a correct answer.