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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 358 · 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.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest 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.Can a triangle have sides of 2 cm, 6 cm and 7 cm? (a) Yes (b) No
  4. 4.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 9 cm, 7 cm and 19 cm? (a) No (b) Yes
  9. 9.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  10. 10.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  14. 14.Can a triangle have sides of 2 cm, 2 cm and 8 cm? (a) Yes (b) No
  15. 15.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (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 triangle ABC, angle A = 54° and angle B = 59°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 72° and angle B = 80°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  25. 25.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  26. 26.Can a triangle have sides of 7 cm, 8 cm and 10 cm? (a) No (b) Yes
  27. 27.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  28. 28.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  29. 29.Can a triangle have sides of 8 cm, 10 cm and 10 cm? (a) Yes (b) No
  30. 30.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  35. 35.Can a triangle have sides of 10 cm, 1 cm and 10 cm? (a) No (b) Yes
  36. 36.In triangle ABC, angle A = 90° and angle B = 42°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 4 cm, 9 cm and 10 cm? (a) No (b) Yes
  39. 39.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 86° and angle B = 64°. What is angle C (in degrees)?

Answer key

  1. 72
  2. 30
  3. Yes
  4. 22
  5. 57
  6. 10
  7. 78
  8. No
  9. 15
  10. 43
  11. 79
  12. 138
  13. 25
  14. No
  15. 11
  16. 14
  17. 58
  18. 36
  19. 67
  20. 36
  21. 32
  22. 112
  23. 28
  24. 86
  25. 24
  26. Yes
  27. 37
  28. 22
  29. Yes
  30. 70
  31. 29
  32. 100
  33. 76
  34. 36
  35. Yes
  36. 48
  37. 90
  38. Yes
  39. 57
  40. 30

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