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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 250 · 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.Can a triangle have sides of 12 cm, 12 cm and 2 cm? (a) Yes (b) No
  2. 2.Can a triangle have sides of 20 cm, 11 cm and 9 cm? (a) Yes (b) No
  3. 3.The two interior opposite angles of a triangle are 30° and 73°. What is the exterior angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 74° and 27°. What is the exterior angle (in degrees)?
  5. 5.In triangle ABC, angle A = 60° and angle B = 81°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 147°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 8 cm, 8 cm and 4 cm? (a) No (b) Yes
  8. 8.The two interior opposite angles of a triangle are 20° and 64°. What is the exterior angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  10. 10.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 35° and 57°. What is the exterior angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  15. 15.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  16. 16.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  17. 17.In triangle ABC, angle A = 50° and angle B = 92°. What is angle C (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  20. 20.Can a triangle have sides of 18 cm, 10 cm and 8 cm? (a) Yes (b) No
  21. 21.In triangle ABC, angle A = 42° and angle B = 54°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 6 cm, 4 cm and 13 cm? (a) No (b) Yes
  24. 24.Can a triangle have sides of 7 cm, 5 cm and 6 cm? (a) No (b) Yes
  25. 25.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 44° and angle B = 65°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 35° and angle B = 59°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 18 cm, 2 cm and 12 cm? (a) No (b) Yes
  29. 29.Can a triangle have sides of 9 cm, 22 cm and 9 cm? (a) No (b) Yes
  30. 30.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 22 cm, 10 cm and 10 cm? (a) No (b) Yes
  32. 32.The two interior opposite angles of a triangle are 39° and 77°. What is the exterior angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  37. 37.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 27° and 36°. What is the exterior angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 48° and 60°. What is the exterior angle (in degrees)?

Answer key

  1. Yes
  2. No
  3. 103
  4. 101
  5. 39
  6. 67
  7. Yes
  8. 84
  9. 20
  10. 56
  11. 92
  12. 61
  13. 55
  14. 25
  15. 32
  16. 3
  17. 38
  18. 17
  19. 61
  20. No
  21. 84
  22. 126
  23. No
  24. Yes
  25. 70
  26. 71
  27. 86
  28. No
  29. No
  30. 54
  31. No
  32. 116
  33. 72
  34. 90
  35. 100
  36. 26
  37. 66
  38. 63
  39. 102
  40. 108

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