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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 94 · 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 triangle ABC, angle A = 91° and angle B = 26°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 41° and angle B = 21°. What is angle C (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.In triangle ABC, angle A = 42° and angle B = 106°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  9. 9.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 71° and angle B = 41°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 61° and 26°. What is the exterior angle (in degrees)?
  18. 18.In triangle ABC, angle A = 56° and angle B = 46°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 12 cm, 22 cm and 10 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  23. 23.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 39° and 56°. What is the exterior angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  27. 27.In triangle ABC, angle A = 31° and angle B = 21°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  31. 31.The two interior opposite angles of a triangle are 33° and 75°. What is the exterior angle (in degrees)?
  32. 32.In triangle ABC, angle A = 39° and angle B = 105°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 8 cm, 16 cm and 3 cm? (a) No (b) Yes
  34. 34.Can a triangle have sides of 9 cm, 10 cm and 23 cm? (a) No (b) Yes
  35. 35.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  38. 38.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?

Answer key

  1. 63
  2. 118
  3. 39
  4. 32
  5. 40
  6. 17
  7. 90
  8. 72
  9. 30
  10. 65
  11. 15
  12. 29
  13. 82
  14. 33
  15. 68
  16. 69
  17. 87
  18. 78
  19. 26
  20. 67
  21. No
  22. 20
  23. 57
  24. 95
  25. 90
  26. 25
  27. 128
  28. 53
  29. 14
  30. 25
  31. 108
  32. 36
  33. No
  34. No
  35. 68
  36. 90
  37. 39
  38. 36
  39. 20
  40. 20

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