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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 299 · 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 80°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 12 cm, 25 cm and 10 cm? (a) Yes (b) No
  3. 3.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 80° and 56°. What is the exterior angle (in degrees)?
  7. 7.Can a triangle have sides of 5 cm, 12 cm and 17 cm? (a) No (b) Yes
  8. 8.In triangle ABC, angle A = 43° and angle B = 55°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  10. 10.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  11. 11.In triangle ABC, angle A = 69° and angle B = 32°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 20 cm, 10 cm and 6 cm? (a) Yes (b) No
  16. 16.Can a triangle have sides of 9 cm, 10 cm and 8 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.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 52° and angle B = 29°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 17 cm and 3 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  23. 23.In triangle ABC, angle A = 59° and angle B = 66°. What is angle C (in degrees)?
  24. 24.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  25. 25.In triangle ABC, angle A = 90° and angle B = 53°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 71° and angle B = 84°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 66° and angle B = 47°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  30. 30.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 35° and angle B = 75°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  34. 34.Can a triangle have sides of 12 cm, 10 cm and 2 cm? (a) No (b) Yes
  35. 35.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 55° and 65°. What is the exterior angle (in degrees)?
  38. 38.Can a triangle have sides of 12 cm, 8 cm and 24 cm? (a) Yes (b) No
  39. 39.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?

Answer key

  1. 10
  2. No
  3. 38
  4. 50
  5. 32
  6. 136
  7. No
  8. 82
  9. 60
  10. 20
  11. 79
  12. 50
  13. 66
  14. 42
  15. No
  16. Yes
  17. 40
  18. 136
  19. 28
  20. 99
  21. No
  22. 48
  23. 55
  24. 30
  25. 37
  26. 90
  27. 25
  28. 67
  29. 77
  30. 31
  31. 26
  32. 70
  33. 72
  34. No
  35. 58
  36. 22
  37. 120
  38. No
  39. 40
  40. 90

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