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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 845 · 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 two interior opposite angles of a triangle are 47° and 69°. What is the exterior angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 85° and angle B = 34°. What is angle C (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 50° and 45°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 97° and angle B = 31°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  9. 9.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)?
  10. 10.In triangle ABC, angle A = 87° and angle B = 37°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest 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 a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 57° and angle B = 75°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  21. 21.In triangle ABC, angle A = 36° and angle B = 121°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 44° and 52°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 7 cm, 4 cm and 16 cm? (a) Yes (b) No
  26. 26.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  27. 27.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 84° and angle B = 71°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  32. 32.In triangle ABC, angle A = 27° and angle B = 99°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (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.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  38. 38.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 31° and angle B = 86°. What is angle C (in degrees)?

Answer key

  1. 116
  2. 21
  3. 45
  4. 50
  5. 61
  6. 95
  7. 52
  8. 18
  9. 8
  10. 56
  11. 90
  12. 29
  13. 29
  14. 30
  15. 43
  16. 15
  17. 48
  18. 72
  19. 66
  20. 25
  21. 23
  22. 84
  23. 96
  24. 63
  25. No
  26. 51
  27. 28
  28. 25
  29. 20
  30. 122
  31. 39
  32. 54
  33. 58
  34. 20
  35. 36
  36. 49
  37. 26
  38. 132
  39. 75
  40. 63

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