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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 995 · 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.

NameDateTime takenScore ___ / 40
  1. 1.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 61° and angle B = 75°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 6 cm, 6 cm and 5 cm? (a) No (b) Yes
  5. 5.Can a triangle have sides of 17 cm, 10 cm and 10 cm? (a) Yes (b) No
  6. 6.The two interior opposite angles of a triangle are 23° and 35°. What is the exterior angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.Can a triangle have sides of 4 cm, 10 cm and 10 cm? (a) No (b) Yes
  9. 9.In triangle ABC, angle A = 74° and angle B = 24°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  14. 14.In triangle ABC, angle A = 71° and angle B = 33°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  16. 16.In triangle ABC, angle A = 66° and angle B = 51°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 2 cm, 18 cm and 12 cm? (a) No (b) Yes
  18. 18.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  20. 20.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 11 cm and 12 cm? (a) No (b) Yes
  22. 22.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 95° and angle B = 24°. What is angle C (in degrees)?
  26. 26.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  29. 29.In triangle ABC, angle A = 97° and angle B = 23°. What is angle C (in degrees)?
  30. 30.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 78° and 31°. What is the exterior angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 69° and angle B = 56°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 13 cm, 3 cm and 5 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 25° and angle B = 20°. What is angle C (in degrees)?

Answer key

  1. 55
  2. 44
  3. 112
  4. Yes
  5. Yes
  6. 58
  7. 25
  8. Yes
  9. 82
  10. 28
  11. 45
  12. 40
  13. 80
  14. 76
  15. 50
  16. 63
  17. No
  18. 11
  19. 13
  20. 49
  21. Yes
  22. 13
  23. 45
  24. 25
  25. 61
  26. 22
  27. 24
  28. 59
  29. 60
  30. 50
  31. 109
  32. 80
  33. 20
  34. 55
  35. 39
  36. 47
  37. 30
  38. No
  39. 106
  40. 135

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