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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 530 · 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 triangle ABC, angle A = 78° and angle B = 78°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  4. 4.Can a triangle have sides of 7 cm, 11 cm and 11 cm? (a) Yes (b) No
  5. 5.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 24° and angle B = 61°. What is angle C (in degrees)?
  7. 7.Can a triangle have sides of 8 cm, 7 cm and 14 cm? (a) Yes (b) No
  8. 8.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  9. 9.Can a triangle have sides of 5 cm, 16 cm and 6 cm? (a) Yes (b) No
  10. 10.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 77° and angle B = 80°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  21. 21.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  23. 23.In triangle ABC, angle A = 98° and angle B = 35°. What is angle C (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  25. 25.Can a triangle have sides of 10 cm, 12 cm and 22 cm? (a) Yes (b) No
  26. 26.Can a triangle have sides of 3 cm, 10 cm and 11 cm? (a) No (b) Yes
  27. 27.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  29. 29.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  32. 32.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  34. 34.Can a triangle have sides of 11 cm, 6 cm and 13 cm? (a) No (b) Yes
  35. 35.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 63° and 23°. What is the exterior angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  38. 38.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?

Answer key

  1. 24
  2. 124
  3. 84
  4. Yes
  5. 16
  6. 95
  7. Yes
  8. 11
  9. No
  10. 61
  11. 30
  12. 23
  13. 47
  14. 79
  15. 54
  16. 32
  17. 72
  18. 54
  19. 90
  20. 25
  21. 12
  22. 72
  23. 47
  24. 39
  25. No
  26. Yes
  27. 68
  28. 66
  29. 44
  30. 59
  31. 24
  32. 68
  33. 100
  34. Yes
  35. 90
  36. 86
  37. 25
  38. 68
  39. 50
  40. 42

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