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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 430 · 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.Can a triangle have sides of 6 cm, 4 cm and 6 cm? (a) No (b) Yes
  2. 2.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 62° and angle B = 68°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  5. 5.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 90° and angle B = 44°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  8. 8.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 21° and angle B = 110°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  18. 18.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)?
  19. 19.In triangle ABC, angle A = 34° and angle B = 115°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  21. 21.In triangle ABC, angle A = 84° and angle B = 31°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 9 cm, 11 cm and 5 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 67° and angle B = 37°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 65° and angle B = 72°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 10 cm, 5 cm and 8 cm? (a) No (b) Yes
  26. 26.Can a triangle have sides of 17 cm, 5 cm and 12 cm? (a) No (b) Yes
  27. 27.In triangle ABC, angle A = 46° and angle B = 78°. What is angle C (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  29. 29.An exterior angle of a triangle is 150°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  30. 30.In triangle ABC, angle A = 70° and angle B = 50°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 85° and angle B = 68°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 48° and angle B = 30°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 57° and angle B = 25°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 3 cm, 11 cm and 3 cm? (a) Yes (b) No
  38. 38.In triangle ABC, angle A = 72° and angle B = 63°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  40. 40.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?

Answer key

  1. Yes
  2. 61
  3. 50
  4. 17
  5. 26
  6. 46
  7. 120
  8. 56
  9. 40
  10. 32
  11. 36
  12. 31
  13. 36
  14. 37
  15. 49
  16. 21
  17. 22
  18. 15
  19. 31
  20. 13
  21. 65
  22. Yes
  23. 76
  24. 43
  25. Yes
  26. No
  27. 56
  28. 25
  29. 78
  30. 60
  31. 128
  32. 27
  33. 45
  34. 60
  35. 102
  36. 98
  37. No
  38. 45
  39. 62
  40. 31

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