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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 585 · 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 98°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 4 cm and 6 cm? (a) Yes (b) No
  3. 3.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  7. 7.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)?
  8. 8.Can a triangle have sides of 17 cm, 4 cm and 10 cm? (a) No (b) Yes
  9. 9.In triangle ABC, angle A = 68° and angle B = 39°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 59° and 25°. What is the exterior angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  15. 15.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  16. 16.The two interior opposite angles of a triangle are 65° and 48°. What is the exterior angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 72° and angle B = 24°. What is angle C (in degrees)?
  19. 19.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 84° and angle B = 34°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 81° and angle B = 42°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 70° and angle B = 80°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 9 cm, 25 cm and 11 cm? (a) No (b) Yes
  29. 29.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  30. 30.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  32. 32.In triangle ABC, angle A = 66° and angle B = 80°. What is angle C (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 56° and 24°. What is the exterior angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  35. 35.Can a triangle have sides of 8 cm, 5 cm and 11 cm? (a) No (b) Yes
  36. 36.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 84° and angle B = 53°. What is angle C (in degrees)?

Answer key

  1. 58
  2. Yes
  3. 50
  4. 36
  5. 130
  6. 84
  7. 15
  8. No
  9. 73
  10. 16
  11. 60
  12. 24
  13. 84
  14. 17
  15. 25
  16. 113
  17. 76
  18. 84
  19. 70
  20. 62
  21. 57
  22. 49
  23. 57
  24. 5
  25. 30
  26. 52
  27. 42
  28. No
  29. 24
  30. 15
  31. 25
  32. 34
  33. 80
  34. 17
  35. Yes
  36. 78
  37. 90
  38. 90
  39. 75
  40. 43

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