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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 633 · 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 an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 66° and angle B = 38°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 81° and angle B = 33°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  9. 9.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  12. 12.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 35° and angle B = 123°. What is angle C (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 73° and 71°. What is the exterior angle (in degrees)?
  17. 17.Can a triangle have sides of 8 cm, 17 cm and 9 cm? (a) Yes (b) No
  18. 18.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  20. 20.Can a triangle have sides of 5 cm, 9 cm and 7 cm? (a) No (b) Yes
  21. 21.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  23. 23.The two interior opposite angles of a triangle are 61° and 30°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  26. 26.Can a triangle have sides of 12 cm, 12 cm and 7 cm? (a) No (b) Yes
  27. 27.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)?
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 31° and 23°. What is the exterior angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 87° and angle B = 54°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 48° and angle B = 60°. What is angle C (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 24° and 72°. What is the exterior angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?

Answer key

  1. 40
  2. 70
  3. 18
  4. 22
  5. 50
  6. 76
  7. 66
  8. 20
  9. 32
  10. 79
  11. 17
  12. 40
  13. 92
  14. 68
  15. 22
  16. 144
  17. No
  18. 37
  19. 10
  20. Yes
  21. 50
  22. 39
  23. 91
  24. 69
  25. 41
  26. Yes
  27. 8
  28. 36
  29. 42
  30. 57
  31. 56
  32. 54
  33. 80
  34. 39
  35. 80
  36. 112
  37. 75
  38. 72
  39. 96
  40. 30

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