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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 33 · 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.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 99° and angle B = 35°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 49° and angle B = 47°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 23° and 60°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 2 cm, 14 cm and 9 cm? (a) Yes (b) No
  7. 7.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  9. 9.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 10 cm, 9 cm and 9 cm? (a) Yes (b) No
  11. 11.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  12. 12.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  14. 14.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  15. 15.Can a triangle have sides of 6 cm, 9 cm and 2 cm? (a) Yes (b) No
  16. 16.In triangle ABC, angle A = 45° and angle B = 76°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 62° and angle B = 50°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 83° and angle B = 29°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 11 cm, 12 cm and 8 cm? (a) No (b) Yes
  22. 22.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  28. 28.Can a triangle have sides of 10 cm, 22 cm and 10 cm? (a) Yes (b) No
  29. 29.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  31. 31.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)?
  32. 32.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 65° and 79°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 41° and angle B = 41°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 4 cm, 6 cm and 2 cm? (a) Yes (b) No
  37. 37.Can a triangle have sides of 7 cm, 18 cm and 7 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  39. 39.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)?
  40. 40.In triangle ABC, angle A = 70° and angle B = 82°. What is angle C (in degrees)?

Answer key

  1. 24
  2. 46
  3. 84
  4. 72
  5. 83
  6. No
  7. 36
  8. 17
  9. 64
  10. Yes
  11. 90
  12. 46
  13. 70
  14. 8
  15. No
  16. 59
  17. 25
  18. 68
  19. 68
  20. 31
  21. Yes
  22. 25
  23. 40
  24. 76
  25. 66
  26. 28
  27. 45
  28. No
  29. 52
  30. 20
  31. 24
  32. 25
  33. 30
  34. 144
  35. 98
  36. No
  37. No
  38. 90
  39. 15
  40. 28

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