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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 349 · 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 90°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 59° and angle B = 44°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  4. 4.Can a triangle have sides of 7 cm, 12 cm and 19 cm? (a) Yes (b) No
  5. 5.In triangle ABC, angle A = 24° and angle B = 52°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 80° and angle B = 79°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 53° and angle B = 36°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 27° and angle B = 25°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 18 cm, 8 cm and 7 cm? (a) Yes (b) No
  14. 14.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 40° and angle B = 47°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 28° and angle B = 131°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  18. 18.Can a triangle have sides of 7 cm, 13 cm and 4 cm? (a) Yes (b) No
  19. 19.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  25. 25.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 79° and 39°. What is the exterior angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  28. 28.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 62° and angle B = 65°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  38. 38.Can a triangle have sides of 14 cm, 8 cm and 2 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 7 cm, 9 cm and 11 cm? (a) No (b) Yes
  40. 40.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?

Answer key

  1. 21
  2. 77
  3. 20
  4. No
  5. 104
  6. 21
  7. 91
  8. 54
  9. 59
  10. 34
  11. 74
  12. 128
  13. No
  14. 59
  15. 93
  16. 21
  17. 90
  18. No
  19. 34
  20. 120
  21. 78
  22. 66
  23. 30
  24. 72
  25. 39
  26. 118
  27. 5
  28. 38
  29. 17
  30. 42
  31. 40
  32. 47
  33. 53
  34. 20
  35. 25
  36. 39
  37. 13
  38. No
  39. Yes
  40. 45

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