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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 864 · 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 2 : 2 : 5. What is the biggest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 46° and angle B = 48°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 50° and angle B = 109°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 2 cm, 2 cm and 9 cm? (a) Yes (b) No
  6. 6.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  13. 13.In triangle ABC, angle A = 79° and angle B = 61°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 68° and 69°. What is the exterior angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 30° and 27°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 13 cm, 9 cm and 4 cm? (a) Yes (b) No
  17. 17.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 80° and 42°. What is the exterior angle (in degrees)?
  22. 22.In triangle ABC, angle A = 54° and angle B = 102°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 99° and angle B = 25°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 77° and angle B = 43°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  28. 28.In triangle ABC, angle A = 68° and angle B = 88°. What is angle C (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  31. 31.Can a triangle have sides of 7 cm, 11 cm and 23 cm? (a) Yes (b) No
  32. 32.Can a triangle have sides of 10 cm, 23 cm and 12 cm? (a) No (b) Yes
  33. 33.In triangle ABC, angle A = 77° and angle B = 63°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  37. 37.In triangle ABC, angle A = 80° and angle B = 22°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?

Answer key

  1. 100
  2. 86
  3. 18
  4. 21
  5. No
  6. 8
  7. 16
  8. 90
  9. 90
  10. 20
  11. 72
  12. 17
  13. 40
  14. 137
  15. 57
  16. No
  17. 72
  18. 40
  19. 72
  20. 42
  21. 122
  22. 24
  23. 56
  24. 60
  25. 23
  26. 116
  27. 7
  28. 24
  29. 25
  30. 36
  31. No
  32. No
  33. 40
  34. 12
  35. 13
  36. 45
  37. 78
  38. 48
  39. 50
  40. 18

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