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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 924 · 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 44° and 31°. What is the exterior angle (in degrees)?
  2. 2.In triangle ABC, angle A = 20° and angle B = 97°. What is angle C (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  7. 7.In triangle ABC, angle A = 80° and angle B = 65°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  9. 9.Can a triangle have sides of 3 cm, 4 cm and 3 cm? (a) No (b) Yes
  10. 10.Can a triangle have sides of 3 cm, 8 cm and 2 cm? (a) No (b) Yes
  11. 11.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  12. 12.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  16. 16.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)?
  17. 17.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  18. 18.In triangle ABC, angle A = 80° and angle B = 35°. What is angle C (in degrees)?
  19. 19.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  20. 20.Can a triangle have sides of 7 cm, 12 cm and 4 cm? (a) Yes (b) No
  21. 21.The two interior opposite angles of a triangle are 58° and 49°. What is the exterior angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 21° and 40°. What is the exterior angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  28. 28.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  30. 30.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  33. 33.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 30° and 26°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 2 cm, 5 cm and 3 cm? (a) Yes (b) No
  38. 38.In triangle ABC, angle A = 27° and angle B = 118°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 1 cm, 9 cm and 9 cm? (a) Yes (b) No
  40. 40.In triangle ABC, angle A = 43° and angle B = 87°. What is angle C (in degrees)?

Answer key

  1. 75
  2. 63
  3. 20
  4. 120
  5. 59
  6. 11
  7. 35
  8. 13
  9. Yes
  10. No
  11. 10
  12. 80
  13. 39
  14. 71
  15. 40
  16. 8
  17. 38
  18. 65
  19. 45
  20. No
  21. 107
  22. 75
  23. 18
  24. 61
  25. 66
  26. 44
  27. 90
  28. 54
  29. 90
  30. 10
  31. 44
  32. 80
  33. 31
  34. 32
  35. 36
  36. 56
  37. No
  38. 35
  39. Yes
  40. 50

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