Geometry: Common Core (15th Edition)

Published by Prentice Hall
ISBN 10: 0133281159
ISBN 13: 978-0-13328-115-6

Chapter 3 - Parallel and Perpendicular Lines - Common Core Cumulative Standards Review - Selected Response - Page 214: 15


The third angle measures $54.5^{\circ}$.

Work Step by Step

We know that the three interior angles of a triangle equal $180$. If we are already given two of the angles, we can figure out the third angle. Let us set up the equation to add the three angles together. One angle measures $54.5$, and the other measures $71$. Let $x$ be the measure of the last angle: $54.5 + 71 + x = 180$ Let's add the constants together on the left side of the equation to simplify: $125.5 + x = 180$ To solve for $x$, subtract $125.5$ from each side of the equation: $125.5 - 125.5 + x = 180 - 125.5$ Subtract to simplify: $x = 54.5$ The third angle measures $54.5$.
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