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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 996 · 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.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 2 cm, 7 cm and 7 cm? (a) Yes (b) No
  3. 3.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 57° and angle B = 70°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 58° and angle B = 73°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  10. 10.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  11. 11.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 41° and 27°. What is the exterior angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 9 cm, 4 cm and 9 cm? (a) Yes (b) No
  16. 16.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 52° and angle B = 72°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  19. 19.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)?
  20. 20.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 24° and 24°. What is the exterior angle (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 20 cm and 10 cm? (a) Yes (b) No
  23. 23.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 7 cm, 17 cm and 7 cm? (a) No (b) Yes
  25. 25.The two interior opposite angles of a triangle are 27° and 47°. What is the exterior angle (in degrees)?
  26. 26.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  28. 28.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  29. 29.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)?
  30. 30.In triangle ABC, angle A = 43° and angle B = 64°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 24° and 78°. What is the exterior angle (in degrees)?
  33. 33.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  34. 34.Can a triangle have sides of 8 cm, 10 cm and 10 cm? (a) Yes (b) No
  35. 35.In triangle ABC, angle A = 35° and angle B = 52°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  37. 37.Can a triangle have sides of 4 cm, 9 cm and 12 cm? (a) Yes (b) No
  38. 38.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  39. 39.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  40. 40.The two interior opposite angles of a triangle are 50° and 43°. What is the exterior angle (in degrees)?

Answer key

  1. 73
  2. Yes
  3. 13
  4. 29
  5. 53
  6. 66
  7. 30
  8. 49
  9. 75
  10. 61
  11. 5
  12. 12
  13. 68
  14. 65
  15. Yes
  16. 90
  17. 56
  18. 69
  19. 15
  20. 52
  21. 48
  22. No
  23. 86
  24. No
  25. 74
  26. 16
  27. 90
  28. 54
  29. 8
  30. 73
  31. 40
  32. 102
  33. 25
  34. Yes
  35. 93
  36. 25
  37. Yes
  38. 31
  39. 12
  40. 93

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