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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 16 · 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 angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  2. 2.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  3. 3.In triangle ABC, angle A = 36° and angle B = 26°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  5. 5.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 57° and angle B = 102°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 2 cm, 8 cm and 14 cm? (a) Yes (b) No
  12. 12.Can a triangle have sides of 4 cm, 7 cm and 6 cm? (a) No (b) Yes
  13. 13.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 80° and angle B = 44°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 47° and angle B = 107°. What is angle C (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  17. 17.In triangle ABC, angle A = 57° and angle B = 74°. What is angle C (in degrees)?
  18. 18.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 74°. What is the other one (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.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 4 cm and 8 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 64° and angle B = 60°. What is angle C (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  25. 25.Can a triangle have sides of 11 cm, 19 cm and 6 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 54° and angle B = 22°. What is angle C (in degrees)?
  27. 27.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)?
  28. 28.Can a triangle have sides of 3 cm, 4 cm and 4 cm? (a) Yes (b) No
  29. 29.The two interior opposite angles of a triangle are 77° and 35°. What is the exterior angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 8 cm, 4 cm and 3 cm? (a) No (b) Yes
  33. 33.In triangle ABC, angle A = 57° and angle B = 80°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 22° and angle B = 134°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 73° and 51°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 93° and angle B = 65°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 30° and angle B = 60°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 3 cm, 11 cm and 12 cm? (a) No (b) Yes
  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. 20
  3. 118
  4. 20
  5. 24
  6. 40
  7. 20
  8. 68
  9. 10
  10. 21
  11. No
  12. Yes
  13. 45
  14. 56
  15. 26
  16. 10
  17. 49
  18. 47
  19. 90
  20. 64
  21. 72
  22. Yes
  23. 56
  24. 20
  25. No
  26. 104
  27. 7
  28. Yes
  29. 112
  30. 61
  31. 38
  32. No
  33. 43
  34. 54
  35. 24
  36. 124
  37. 22
  38. 90
  39. Yes
  40. 90

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