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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 932 · 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 a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  5. 5.Can a triangle have sides of 8 cm, 5 cm and 7 cm? (a) Yes (b) No
  6. 6.An exterior angle of a triangle is 46°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  7. 7.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  8. 8.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  9. 9.Can a triangle have sides of 3 cm, 9 cm and 17 cm? (a) Yes (b) No
  10. 10.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 49° and angle B = 70°. What is angle C (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 21° and 20°. What is the exterior angle (in degrees)?
  13. 13.In triangle ABC, angle A = 24° and angle B = 85°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 59° and angle B = 79°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 48° and 67°. What is the exterior angle (in degrees)?
  21. 21.Can a triangle have sides of 10 cm, 9 cm and 3 cm? (a) No (b) Yes
  22. 22.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  23. 23.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  26. 26.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 77° and angle B = 69°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 4 cm, 2 cm and 4 cm? (a) Yes (b) No
  30. 30.The two interior opposite angles of a triangle are 76° and 66°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 9 cm, 6 cm and 19 cm? (a) Yes (b) No
  33. 33.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  38. 38.Can a triangle have sides of 4 cm, 3 cm and 2 cm? (a) Yes (b) No
  39. 39.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?

Answer key

  1. 13
  2. 30
  3. 31
  4. 72
  5. Yes
  6. 26
  7. 27
  8. 20
  9. No
  10. 116
  11. 61
  12. 41
  13. 71
  14. 34
  15. 20
  16. 28
  17. 42
  18. 36
  19. 72
  20. 115
  21. Yes
  22. 21
  23. 42
  24. 50
  25. 26
  26. 69
  27. 30
  28. 34
  29. Yes
  30. 142
  31. 90
  32. No
  33. 38
  34. 104
  35. 45
  36. 75
  37. 25
  38. Yes
  39. 78
  40. 66

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