4.7.E
The Standard
determine the measure of an unknown angle formed by two non-overlapping adjacent angles given one or both angle measures
Texas Essential Knowledge and Skills for Mathematics
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students use the fact that two adjacent angle measures add to the measure of the whole angle. They add or subtract to find a missing part or the total.
What Mastery Looks Like
- Students identify the whole angle and its two adjacent parts. They add to find the whole or subtract a known part from the whole, then check that the parts combine correctly.
Common Misconceptions
- Students may add when they should subtract, especially when the whole angle is given. They may also subtract the smaller number from the larger without identifying the whole and the known part.
How to Assess It
- Give this exit ticket: “A 95° angle is split into angles measuring 38° and x°. Find x and write the equation you used.”
Lesson moves
Ways to Teach It
Give students paper angle wedges labeled with measures, then have them combine two wedges and calculate the total angle.
Ask students to explain why a 90° angle split into 35° and x° can be solved with subtraction.
Create matching cards with angle diagrams, equations, and missing measures for students to pair in small groups.
Use intersecting sidewalk or road diagrams to find an unknown turn angle from a total angle and one known part.
Keep exploring
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draw an angle with a given measure
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