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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 202 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

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  1. 1.In triangle ABC, angle A = 36° and angle B = 101°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  5. 5.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  6. 6.The two interior opposite angles of a triangle are 26° and 75°. What is the exterior angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  10. 10.The two interior opposite angles of a triangle are 54° and 23°. What is the exterior angle (in degrees)?
  11. 11.In triangle ABC, angle A = 33° and angle B = 31°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  14. 14.Can a triangle have sides of 11 cm, 5 cm and 3 cm? (a) Yes (b) No
  15. 15.The two interior opposite angles of a triangle are 48° and 35°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 17 cm, 9 cm and 8 cm? (a) No (b) Yes
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 48° and 52°. What is the exterior angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  22. 22.Can a triangle have sides of 12 cm, 7 cm and 20 cm? (a) No (b) Yes
  23. 23.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  24. 24.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  25. 25.The two interior opposite angles of a triangle are 57° and 26°. What is the exterior angle (in degrees)?
  26. 26.Can a triangle have sides of 10 cm, 3 cm and 8 cm? (a) Yes (b) No
  27. 27.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  30. 30.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 80° and 72°. What is the exterior angle (in degrees)?
  34. 34.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  37. 37.In triangle ABC, angle A = 35° and angle B = 68°. What is angle C (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  39. 39.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  40. 40.The two interior opposite angles of a triangle are 74° and 63°. What is the exterior angle (in degrees)?

Answer key

  1. 43
  2. 38
  3. 70
  4. 32
  5. 7
  6. 101
  7. 12
  8. 74
  9. 25
  10. 77
  11. 116
  12. 67
  13. 36
  14. No
  15. 83
  16. No
  17. 30
  18. 75
  19. 100
  20. 18
  21. 17
  22. No
  23. 77
  24. 15
  25. 83
  26. Yes
  27. 64
  28. 74
  29. 42
  30. 36
  31. 120
  32. 73
  33. 152
  34. 34
  35. 12
  36. 15
  37. 77
  38. 17
  39. 10
  40. 137

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