Geometry
Supplementary angles worksheets
Find one missing angle in 6, 8 or 10 supplementary pairs using whole numbers, tenths or hundredths. Each numbered straight-line diagram identifies the given and unknown regions clearly.
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Triangle angle sum worksheets
Solve eight exact triangle angle equations with one variable expression and two numeric givens. Choose interior, exterior or mixed placement independently from single-variable, algebraic or mixed expression practice.
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Match each numbered sector to its listed value. Use the correct triangle, adjacent exterior or vertical relationship to solve for x. Diagrams are not to scale.
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Customize this worksheetConnect numbered sectors to an exact equation
Every sheet has eight schematic triangles. Match Angle 1, Angle 2 and Angle 3 in the list to the numbered sectors in the diagram, then write an equation using the interior-angle sum, an adjacent exterior angle or a vertical-angle proxy.
Exactly one marked angle contains x and the other two are numeric givens. Solve for x and record the variable value without a degree sign. The drawings are intentionally not to scale, so use the printed expressions and stated angle relationship.
Learning objective
What this activity builds
Use the 180-degree interior sum, the adjacent exterior-angle theorem and vertical-angle equality to build and solve a one-variable equation from three numbered sectors.
Worked example
Angles 1 and 2 are 47 degrees and 70 degrees. Angle 3 is the interior expression 3x. What is x?
x = 21.
The three interior angles total 180 degrees, so 47 + 70 + 3x = 180. Subtract 117 to get 3x = 63, then divide by 3. The variable answer is 21, without a degree sign.
Teaching notes
Make the practice count
- Match list numbers to diagram sectors before choosing an equation.
- For three interior or vertical-proxy values, add the three marked values to 180 degrees.
- For an adjacent exterior proxy, set the exterior value equal to the two remote interior values.
- Substitute the solved x back into the printed expression and check every angle remains positive.
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