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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 432 · 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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 6 cm, 11 cm and 15 cm? (a) Yes (b) No
  2. 2.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.In triangle ABC, angle A = 24° and angle B = 87°. What is angle C (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 63° and 63°. What is the exterior angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 21° and angle B = 87°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 20 cm, 11 cm and 5 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 96° and angle B = 20°. What is angle C (in degrees)?
  13. 13.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  16. 16.In triangle ABC, angle A = 63° and angle B = 24°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 9 cm, 2 cm and 8 cm? (a) No (b) Yes
  18. 18.In triangle ABC, angle A = 36° and angle B = 54°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 58° and angle B = 47°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 40° and angle B = 116°. What is angle C (in degrees)?
  21. 21.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 22° and 64°. What is the exterior angle (in degrees)?
  23. 23.In triangle ABC, angle A = 58° and angle B = 58°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  28. 28.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 43° and 35°. What is the exterior angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  31. 31.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  32. 32.Can a triangle have sides of 12 cm, 5 cm and 6 cm? (a) No (b) Yes
  33. 33.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 75° and angle B = 49°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 43° and angle B = 21°. What is angle C (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  38. 38.In triangle ABC, angle A = 21° and angle B = 61°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 39° and angle B = 23°. What is angle C (in degrees)?

Answer key

  1. Yes
  2. 54
  3. 17
  4. 69
  5. 5
  6. 44
  7. 36
  8. 126
  9. 52
  10. 72
  11. No
  12. 64
  13. 10
  14. 63
  15. 10
  16. 93
  17. Yes
  18. 90
  19. 75
  20. 24
  21. 15
  22. 86
  23. 64
  24. 98
  25. 92
  26. 120
  27. 15
  28. 108
  29. 78
  30. 5
  31. 24
  32. No
  33. 21
  34. 56
  35. 62
  36. 116
  37. 30
  38. 98
  39. 10
  40. 118

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