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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 5 · 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 63°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  3. 3.In triangle ABC, angle A = 93° and angle B = 50°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  5. 5.In a right-angled triangle, one of the other two angles is 52°. What is the third 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 longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  8. 8.In triangle ABC, angle A = 53° and angle B = 71°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 7 cm, 7 cm and 12 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 66° and angle B = 89°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  16. 16.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)?
  17. 17.In triangle ABC, angle A = 100° and angle B = 34°. What is angle C (in degrees)?
  18. 18.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  19. 19.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  20. 20.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  22. 22.In triangle ABC, angle A = 62° and angle B = 57°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 12 cm, 26 cm and 10 cm? (a) No (b) Yes
  24. 24.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 76° and angle B = 38°. What is angle C (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  27. 27.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  28. 28.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  30. 30.In triangle ABC, angle A = 66° and angle B = 80°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 66° and 48°. What is the exterior angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 63° and angle B = 39°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 83° and angle B = 67°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 78° and 69°. What is the exterior angle (in degrees)?
  40. 40.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?

Answer key

  1. 27
  2. 46
  3. 37
  4. 26
  5. 38
  6. 17
  7. 12
  8. 56
  9. 25
  10. 61
  11. Yes
  12. 25
  13. 58
  14. 48
  15. 40
  16. 7
  17. 46
  18. 65
  19. 41
  20. 32
  21. 50
  22. 61
  23. No
  24. 50
  25. 66
  26. 17
  27. 26
  28. 90
  29. 74
  30. 34
  31. 75
  32. 20
  33. 114
  34. 90
  35. 102
  36. 78
  37. 30
  38. 34
  39. 147
  40. 73

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