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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 813 · 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.The two interior opposite angles of a triangle are 34° and 58°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  4. 4.In triangle ABC, angle A = 87° and angle B = 23°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 9 cm, 10 cm and 3 cm? (a) Yes (b) No
  6. 6.In triangle ABC, angle A = 79° and angle B = 41°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 28° and 65°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 27° and 29°. What is the exterior angle (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.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  16. 16.Can a triangle have sides of 13 cm, 7 cm and 5 cm? (a) No (b) Yes
  17. 17.In triangle ABC, angle A = 91° and angle B = 49°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 3 cm, 7 cm and 8 cm? (a) Yes (b) No
  19. 19.The two interior opposite angles of a triangle are 48° and 20°. What is the exterior angle (in degrees)?
  20. 20.Can a triangle have sides of 9 cm, 9 cm and 23 cm? (a) Yes (b) No
  21. 21.In triangle ABC, angle A = 27° and angle B = 81°. What is angle C (in degrees)?
  22. 22.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  23. 23.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 76° and angle B = 30°. What is angle C (in degrees)?
  26. 26.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 6 cm, 8 cm and 5 cm? (a) No (b) Yes
  29. 29.The two interior opposite angles of a triangle are 43° and 33°. What is the exterior angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  34. 34.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  35. 35.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)?
  36. 36.The two interior opposite angles of a triangle are 45° and 23°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 8 cm, 21 cm and 8 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?

Answer key

  1. 92
  2. 32
  3. 36
  4. 70
  5. Yes
  6. 60
  7. 42
  8. 38
  9. 93
  10. 134
  11. 90
  12. 56
  13. 36
  14. 25
  15. 22
  16. No
  17. 40
  18. Yes
  19. 68
  20. No
  21. 72
  22. 15
  23. 90
  24. 29
  25. 74
  26. 78
  27. 126
  28. Yes
  29. 76
  30. 40
  31. 69
  32. 50
  33. 17
  34. 74
  35. 15
  36. 68
  37. 17
  38. No
  39. 53
  40. 10

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