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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 505 · 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 two interior opposite angles of a triangle are 71° and 75°. What is the exterior angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  3. 3.Can a triangle have sides of 3 cm, 4 cm and 2 cm? (a) Yes (b) No
  4. 4.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 6 cm, 12 cm and 10 cm? (a) Yes (b) No
  9. 9.The two interior opposite angles of a triangle are 59° and 28°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 73° and angle B = 57°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  12. 12.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)?
  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 14°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 31° and 35°. What is the exterior angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 79° and angle B = 26°. What is angle C (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  23. 23.Can a triangle have sides of 6 cm, 4 cm and 4 cm? (a) No (b) Yes
  24. 24.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 100° and angle B = 29°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 98° and angle B = 46°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 7 cm, 3 cm and 8 cm? (a) No (b) Yes
  33. 33.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)?
  34. 34.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 9 cm, 9 cm and 4 cm? (a) No (b) Yes
  36. 36.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (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 triangle ABC, angle A = 57° and angle B = 61°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?

Answer key

  1. 146
  2. 45
  3. Yes
  4. 50
  5. 39
  6. 70
  7. 34
  8. Yes
  9. 87
  10. 50
  11. 75
  12. 8
  13. 36
  14. 76
  15. 48
  16. 44
  17. 53
  18. 30
  19. 66
  20. 70
  21. 75
  22. 100
  23. Yes
  24. 38
  25. 51
  26. 36
  27. 17
  28. 20
  29. 75
  30. 40
  31. 12
  32. Yes
  33. 24
  34. 68
  35. Yes
  36. 34
  37. 57
  38. 48
  39. 62
  40. 72

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