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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 646 · 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 an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 27° and 50°. What is the exterior angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  5. 5.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 2 cm, 9 cm and 10 cm? (a) No (b) Yes
  8. 8.In triangle ABC, angle A = 84° and angle B = 33°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  11. 11.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  12. 12.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)?
  13. 13.In triangle ABC, angle A = 31° and angle B = 107°. What is angle C (in degrees)?
  14. 14.An exterior angle of a triangle is 135°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 85° and angle B = 31°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 90° and angle B = 21°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 23° and angle B = 130°. What is angle C (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 5 cm, 6 cm and 8 cm? (a) Yes (b) No
  21. 21.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 63° and angle B = 71°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  26. 26.In triangle ABC, angle A = 55° and angle B = 73°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 72° and angle B = 67°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 70° and angle B = 78°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 3 cm, 11 cm and 12 cm? (a) Yes (b) No
  30. 30.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 25° and angle B = 129°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 64° and angle B = 68°. What is angle C (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 60° and 33°. What is the exterior angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?

Answer key

  1. 34
  2. 77
  3. 94
  4. 17
  5. 38
  6. 25
  7. Yes
  8. 63
  9. 47
  10. 31
  11. 36
  12. 15
  13. 42
  14. 55
  15. 19
  16. 64
  17. 69
  18. 27
  19. 79
  20. Yes
  21. 33
  22. 73
  23. 46
  24. 40
  25. 18
  26. 52
  27. 41
  28. 32
  29. Yes
  30. 22
  31. 74
  32. 26
  33. 54
  34. 78
  35. 58
  36. 90
  37. 12
  38. 48
  39. 93
  40. 25

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