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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 943 · 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 angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  4. 4.Can a triangle have sides of 12 cm, 3 cm and 5 cm? (a) No (b) Yes
  5. 5.Can a triangle have sides of 2 cm, 2 cm and 9 cm? (a) Yes (b) No
  6. 6.The angles of a triangle are in the ratio 5 : 6 : 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.In triangle ABC, angle A = 45° and angle B = 69°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 8 cm, 5 cm and 5 cm? (a) No (b) Yes
  10. 10.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 66° and angle B = 91°. What is angle C (in degrees)?
  12. 12.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 87° and angle B = 70°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 40° and angle B = 72°. What is angle C (in degrees)?
  18. 18.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 9 cm, 4 cm and 6 cm? (a) No (b) Yes
  21. 21.The two interior opposite angles of a triangle are 31° and 62°. What is the exterior angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 24° and angle B = 62°. What is angle C (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 35° and 52°. What is the exterior angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 25 cm and 10 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 29° and angle B = 128°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 3 cm, 3 cm and 3 cm? (a) No (b) Yes
  30. 30.In triangle ABC, angle A = 92° and angle B = 61°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 52° and angle B = 72°. What is angle C (in degrees)?
  36. 36.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)?
  37. 37.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 33° and angle B = 67°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  40. 40.Can a triangle have sides of 11 cm, 4 cm and 9 cm? (a) No (b) Yes

Answer key

  1. 21
  2. 20
  3. 100
  4. No
  5. No
  6. 70
  7. 15
  8. 66
  9. Yes
  10. 23
  11. 23
  12. 35
  13. 72
  14. 23
  15. 24
  16. 76
  17. 68
  18. 56
  19. 40
  20. Yes
  21. 93
  22. 18
  23. 67
  24. 94
  25. 87
  26. 68
  27. No
  28. 23
  29. Yes
  30. 27
  31. 16
  32. 74
  33. 72
  34. 25
  35. 56
  36. 8
  37. 69
  38. 80
  39. 36
  40. Yes

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