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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 301 · 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.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 84° and angle B = 70°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 46° and angle B = 55°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 61° and angle B = 98°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 74° and angle B = 70°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  10. 10.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 75° and angle B = 38°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 22° and 30°. What is the exterior angle (in degrees)?
  14. 14.In triangle ABC, angle A = 51° and angle B = 20°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 57° and angle B = 39°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 22° and 79°. What is the exterior angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  22. 22.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 71° and angle B = 23°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 88° and angle B = 70°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 44° and angle B = 100°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 31° and angle B = 112°. What is angle C (in degrees)?
  27. 27.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  29. 29.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 29° and 35°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 7 cm, 3 cm and 5 cm? (a) No (b) Yes
  32. 32.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  38. 38.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?

Answer key

  1. 24
  2. 26
  3. 90
  4. 90
  5. 26
  6. 79
  7. 21
  8. 36
  9. 30
  10. 80
  11. 45
  12. 67
  13. 52
  14. 109
  15. 76
  16. 84
  17. 60
  18. 101
  19. 120
  20. 25
  21. 59
  22. 39
  23. 86
  24. 22
  25. 36
  26. 37
  27. 34
  28. 36
  29. 25
  30. 64
  31. Yes
  32. 20
  33. 56
  34. 118
  35. 62
  36. 18
  37. 13
  38. 32
  39. 38
  40. 90

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