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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 836 · 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 = 26° and angle B = 37°. What is angle C (in degrees)?
  2. 2.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  3. 3.In triangle ABC, angle A = 33° and angle B = 54°. What is angle C (in degrees)?
  4. 4.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)?
  5. 5.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 5 cm, 12 cm and 9 cm? (a) Yes (b) No
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  9. 9.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  12. 12.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  13. 13.Can a triangle have sides of 10 cm, 8 cm and 3 cm? (a) No (b) Yes
  14. 14.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 30° and angle B = 53°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 8 cm, 10 cm and 13 cm? (a) No (b) Yes
  17. 17.In triangle ABC, angle A = 74° and angle B = 24°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 32° and 80°. What is the exterior angle (in degrees)?
  21. 21.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  23. 23.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)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  25. 25.Can a triangle have sides of 10 cm, 10 cm and 6 cm? (a) Yes (b) No
  26. 26.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  27. 27.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 81° and angle B = 25°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  32. 32.In triangle ABC, angle A = 83° and angle B = 25°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 83° and angle B = 67°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 17 cm, 2 cm and 12 cm? (a) Yes (b) No
  35. 35.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 53° and angle B = 27°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 21° and 60°. What is the exterior angle (in degrees)?
  39. 39.In triangle ABC, angle A = 100° and angle B = 55°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 23° and angle B = 40°. What is angle C (in degrees)?

Answer key

  1. 117
  2. 31
  3. 93
  4. 24
  5. 23
  6. Yes
  7. 30
  8. 39
  9. 24
  10. 20
  11. 25
  12. 25
  13. Yes
  14. 80
  15. 97
  16. Yes
  17. 82
  18. 136
  19. 72
  20. 112
  21. 55
  22. 35
  23. 8
  24. 90
  25. Yes
  26. 5
  27. 100
  28. 74
  29. 50
  30. 19
  31. 6
  32. 72
  33. 30
  34. No
  35. 32
  36. 100
  37. 22
  38. 81
  39. 25
  40. 117

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