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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 940 · 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.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)?
  2. 2.In triangle ABC, angle A = 41° and angle B = 65°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 79° and angle B = 79°. What is angle C (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 47° and 48°. What is the exterior angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  9. 9.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 58° and angle B = 21°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  13. 13.In triangle ABC, angle A = 31° and angle B = 110°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 48° and angle B = 58°. What is angle C (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  16. 16.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 4 cm, 4 cm and 4 cm? (a) Yes (b) No
  19. 19.In triangle ABC, angle A = 63° and angle B = 76°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 9 cm, 6 cm and 12 cm? (a) Yes (b) No
  26. 26.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  27. 27.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  28. 28.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  29. 29.In triangle ABC, angle A = 36° and angle B = 102°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 44° and 20°. What is the exterior angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  35. 35.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.Can a triangle have sides of 15 cm, 6 cm and 12 cm? (a) Yes (b) No
  39. 39.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?

Answer key

  1. 36
  2. 74
  3. 22
  4. 95
  5. 36
  6. 72
  7. 59
  8. 90
  9. 69
  10. 101
  11. 37
  12. 17
  13. 39
  14. 74
  15. 25
  16. 15
  17. 39
  18. Yes
  19. 41
  20. 25
  21. 36
  22. 65
  23. 69
  24. 102
  25. Yes
  26. 57
  27. 24
  28. 7
  29. 42
  30. 27
  31. 108
  32. 64
  33. 14
  34. 9
  35. 84
  36. 100
  37. 90
  38. Yes
  39. 48
  40. 60

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