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Grade 10 Triangle Angle Sum & Exterior Angles Worksheet with Answers

Grade 10 (US) · Year 11 (UK) · Class 10 (India) · Math

Unit 3: TrianglesAngles in TrianglesCCSS G-CO.C.10

Using the 180° angle sum and the exterior angle theorem to find missing angles. This free high school worksheet has 12 questions and a full answer key. Print it or save it as a PDF — every answer is checked by code, not guessed.

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Triangle Angle Sum & Exterior Angles

Grade 10 · Math

Score___ / 12

Name

Class

Date

Learning goal: Angles in Triangles · CCSS G-CO.C.10

Directions: Use the pictures to help you. Solve each problem. Show your work, then write your answer in the box.

Example

Two angles of a triangle are 53° and 59°. Find the third angle.

Answer: 68°

RememberAngles in a triangle

abca + b + c = 180°The three angles of any trianglealways add up to 180°.Exterior angle = sum of the two far angles
  1. 1

    A triangle has interior angles 83° and 56°. What is the exterior angle at the third vertex?

    83°56°?
    Answer
  2. 2

    An isosceles triangle has a vertex angle of 20°. What is each base angle?

    Show your work
    Answer
  3. 3

    A triangle has interior angles 33° and 32°. What is the exterior angle at the third vertex?

    33°32°?
    Answer
  4. 4

    Two angles of a triangle are 25° and 90°. Find the third angle.

    25°90°?
    Answer
  5. 5

    Two angles of a triangle are 52° and 52°. Find the third angle.

    52°52°?
    Answer
  6. 6

    An isosceles triangle has a vertex angle of 106°. What is each base angle?

    Show your work
    Answer
  7. 7

    Two angles of a triangle are 47° and 65°. Find the third angle.

    47°65°?
    Answer
  8. 8

    An isosceles triangle has a vertex angle of 148°. What is each base angle?

    Show your work
    Answer
  9. 9

    An isosceles triangle has a vertex angle of 50°. What is each base angle?

    Show your work
    Answer
  10. 10

    A triangle has interior angles 48° and 30°. What is the exterior angle at the third vertex?

    48°30°?
    Answer
  11. 11

    An isosceles triangle has a vertex angle of 42°. What is each base angle?

    Show your work
    Answer
  12. 12

    A triangle has interior angles 29° and 119°. What is the exterior angle at the third vertex?

    29°119°?
    Answer

★ Challenge corner for fast finishers

On a grid, you walk from the bottom-left corner to a point 4 blocks right and 4 blocks up, moving only right or up. How many different shortest paths are there?

How did I do?

Teacher's comments

Free printable worksheets with answer keys · aethelsystems.com/worksheets/math/10/triangle_angles

Answer key (click to show)
  1. 1.139°
  2. 2.80°
  3. 3.65°
  4. 4.65°
  5. 5.76°
  6. 6.37°
  7. 7.68°
  8. 8.16°
  9. 9.65°
  10. 10.78°
  11. 11.69°
  12. 12.148°
  13. ★70 (challenge corner)

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