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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Complementary angles worksheets
Find one missing angle in 9, 12 or 15 complementary pairs using whole numbers, tenths or hundredths. Numbered diagrams show the two regions and a separate answer key preserves every given measure.
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Find the missing measure in each complementary pair. The two regions total 90 degrees. Diagrams are not to scale.
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Customize this worksheetUse exact angle relationships to deduce each blank
Each numbered region connects the diagram to one printed measure or blank. Complementary regions total 90 degrees, supplementary regions on a straight line total 180 degrees, and opposite vertical regions are equal.
The diagrams preserve those relationships but are not drawn to the stated values. Use subtraction or vertical-angle equality, then check the result against the 90-degree or 180-degree total instead of measuring the picture.
Learning objective
What this activity builds
Use the fact that complementary angles total exactly 90 degrees to subtract a given measure and state the missing angle with the requested decimal precision.
Worked example
Region 1 is 37.4 degrees and the two regions are complementary. What is Region 2?
52.6 degrees.
Complementary angles total 90 degrees, so subtract 37.4 from 90.0. The result is 52.6 degrees. The right-angle marker confirms the total; the picture is not a measuring scale.
Teaching notes
Make the practice count
- Write the equation given angle + missing angle = 90 degrees before subtracting.
- Line up decimal places and keep trailing zeros when the worksheet asks for a fixed precision.
- Use the region numbers to connect each printed value or blank with the correct sector.
- Check the result by adding the two measures and confirming an exact total of 90 degrees.
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