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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 468 · 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.

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  1. 1.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 20° and angle B = 40°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  5. 5.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 31° and 43°. What is the exterior angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 23° and 60°. What is the exterior angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 22° and 65°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 94° and angle B = 28°. What is angle C (in degrees)?
  13. 13.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)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 46° and angle B = 110°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 2 cm, 7 cm and 7 cm? (a) No (b) Yes
  17. 17.Can a triangle have sides of 7 cm, 15 cm and 9 cm? (a) No (b) Yes
  18. 18.Can a triangle have sides of 9 cm, 10 cm and 4 cm? (a) No (b) Yes
  19. 19.The two interior opposite angles of a triangle are 34° and 69°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 97° and angle B = 53°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 51° and angle B = 73°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 19 cm, 10 cm and 11 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 40° and angle B = 62°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 3 cm, 13 cm and 10 cm? (a) Yes (b) No
  25. 25.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  26. 26.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 5 cm and 17 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 27° and angle B = 44°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 92° and angle B = 29°. What is angle C (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 48° and 61°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  35. 35.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 33° and 65°. What is the exterior angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  38. 38.The two interior opposite angles of a triangle are 27° and 22°. What is the exterior angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?

Answer key

  1. 59
  2. 120
  3. 90
  4. 10
  5. 90
  6. 36
  7. 51
  8. 74
  9. 54
  10. 83
  11. 87
  12. 58
  13. 5
  14. 19
  15. 24
  16. Yes
  17. Yes
  18. Yes
  19. 103
  20. 30
  21. 56
  22. Yes
  23. 78
  24. No
  25. 24
  26. 80
  27. No
  28. 109
  29. 59
  30. 109
  31. 71
  32. 90
  33. 34
  34. 21
  35. 59
  36. 98
  37. 39
  38. 49
  39. 64
  40. 17

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