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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 892 · 40 sums
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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 = 39° and angle B = 87°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 59° and 57°. What is the exterior angle (in degrees)?
  3. 3.In triangle ABC, angle A = 96° and angle B = 45°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 73° and angle B = 39°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 13 cm, 2 cm and 9 cm? (a) Yes (b) No
  9. 9.Can a triangle have sides of 9 cm, 4 cm and 12 cm? (a) No (b) Yes
  10. 10.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  12. 12.Can a triangle have sides of 10 cm, 7 cm and 11 cm? (a) Yes (b) No
  13. 13.Can a triangle have sides of 12 cm, 25 cm and 10 cm? (a) Yes (b) No
  14. 14.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 77° and angle B = 81°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 7 cm, 7 cm and 7 cm? (a) Yes (b) No
  17. 17.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 38° and 78°. What is the exterior angle (in degrees)?
  19. 19.In triangle ABC, angle A = 30° and angle B = 97°. What is angle C (in degrees)?
  20. 20.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  21. 21.In triangle ABC, angle A = 27° and angle B = 75°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 5 cm, 8 cm and 3 cm? (a) No (b) Yes
  23. 23.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 79° and angle B = 78°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 70° and angle B = 64°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 12 cm, 11 cm and 8 cm? (a) No (b) Yes
  30. 30.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 22° and angle B = 40°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 35° and angle B = 26°. What is angle C (in degrees)?
  33. 33.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  34. 34.In triangle ABC, angle A = 70° and angle B = 75°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  36. 36.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  39. 39.Can a triangle have sides of 11 cm, 8 cm and 20 cm? (a) No (b) Yes
  40. 40.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?

Answer key

  1. 54
  2. 116
  3. 39
  4. 54
  5. 128
  6. 68
  7. 64
  8. No
  9. Yes
  10. 29
  11. 40
  12. Yes
  13. No
  14. 29
  15. 22
  16. Yes
  17. 34
  18. 116
  19. 53
  20. 8
  21. 78
  22. No
  23. 12
  24. 19
  25. 130
  26. 23
  27. 18
  28. 46
  29. Yes
  30. 108
  31. 118
  32. 119
  33. 10
  34. 35
  35. 80
  36. 21
  37. 25
  38. 65
  39. No
  40. 136

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