Virginia SOL 7.MG.2.g
The Standard
Given angle measures in a quadrilateral or triangle, determine unknown angle measures in a similar quadrilateral or triangle.
Virginia Standards of Learning for Mathematics · The student will solve problems and justify relationships of similarity using proportional reasoning.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students match corresponding vertices and angles in similar triangles or quadrilaterals. They use equal corresponding angles and angle sums to find unknown measures and explain their reasoning.
What Mastery Looks Like
- Students correctly match corresponding vertices, even when figures are rotated or reflected. They find unknown angles and justify each answer using corresponding angles or polygon angle sums.
Common Misconceptions
- Students may multiply angle measures by the side-length scale factor instead of keeping corresponding angles equal. They may mismatch vertices after a figure is rotated or reflected, or use 180° as the angle sum for a quadrilateral.
How to Assess It
- Give this exit ticket: Triangle ABC is similar to triangle DEF, with A matching D and B matching E. If A = 48° and B = 67°, find F and explain.
Lesson moves
Ways to Teach It
Give pairs of similar polygon cutouts to rotate, reflect, label, and use to solve for missing angle measures.
Ask students to write how they know corresponding angles stay equal even when similar figures have different sizes or orientations.
Use angle cards and polygon diagrams for a timed matching game, then have partners solve the missing measures.
Show two similar roof truss diagrams and ask students to determine missing joint angles needed for matching construction plans.
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Printable 7.MG.2.g Worksheet
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Related Standards
- 7.MG.3.c
Given a diagram, determine an unknown angle measure in a quadrilateral, using properties of quadrilaterals.
- 7.MG.2.f
Solve a proportion to determine a missing side length of similar quadrilaterals or triangles.
- 7.MG.2.a
Identify corresponding congruent angles of similar quadrilaterals and triangles, through the use of geometric markings.
- 7.MG.3
The student will compare and contrast quadrilaterals based on their properties and determine unknown side lengths and angle measures of quadrilaterals.
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