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Angle Addition Worksheets

Find a missing angle part or whole using the angle addition postulate, with whole numbers, tenths or hundredths and worked answers.

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Find the missing measure. Two adjacent angle parts add to the whole angle.

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US Letter

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A4

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Parts make the whole

Two adjacent angle measures add to the whole angle. Subtract a known part from the whole when one part is missing.

Learning objective

What this activity builds

Add adjacent angle parts or subtract a known part from the whole.

Worked example

Angle ABD is 42.5 degrees and angle DBC is 31.25 degrees. Find angle ABC.

73.75 degrees.

Ray BD lies inside angle ABC, so angle ABD + angle DBC = angle ABC. Add 42.5 + 31.25 = 73.75 degrees.

Teaching notes

Make the practice count

  • The middle letter of an angle name is always the vertex.
  • Identify the two parts and the whole before calculating.
  • Add to find the whole; subtract from the whole to find a missing part.

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Nine three-ray diagrams cover each missing-measure position three times. One diagram has a marked 90-degree whole angle, and decimal precision is configurable.

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Math SheetNameScoreTeacherDateAngle AdditionUse angle addition to find the missing angle measure.1.KPQNAngle KNP =78 degAngle PNQ =29 degAngle KNQ =2.NQRPAngle NPQ =61 degAngle QPR =Angle NPR =93 deg3.WYZXAngle WXY =39 degAngle YXZ =Angle WXZ =123 deg4.SUVTAngle STU =30 degAngle UTV =Angle STV =81 deg5.ACDBAngle ABC =Angle CBD =43 degAngle ABD =90 deg6.JLMKAngle JKL =Angle LKM =41 degAngle JKM =95 deg7.BFHDAngle BDF =42 degAngle FDH =81 degAngle BDH =8.AEGCAngle ACE =57 degAngle ECG =80 degAngle ACG =9.EGHFAngle EFG =Angle GFH =82 degAngle EFH =148 degPart 1 + Part 2 = Whole angle.math-sheet.comPage 1 of 1

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