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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 514 · 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.The two interior opposite angles of a triangle are 40° and 44°. What is the exterior angle (in degrees)?
  2. 2.In triangle ABC, angle A = 32° and angle B = 25°. What is angle C (in degrees)?
  3. 3.Can a triangle have sides of 11 cm, 10 cm and 9 cm? (a) No (b) Yes
  4. 4.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 8 cm, 7 cm and 3 cm? (a) No (b) Yes
  7. 7.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  8. 8.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  9. 9.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  10. 10.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  11. 11.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  13. 13.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 67° and 40°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 72° and angle B = 73°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 61° and angle B = 21°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 22° and angle B = 42°. What is angle C (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  20. 20.Can a triangle have sides of 14 cm, 7 cm and 4 cm? (a) No (b) Yes
  21. 21.Can a triangle have sides of 10 cm, 4 cm and 3 cm? (a) Yes (b) No
  22. 22.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 34° and 48°. What is the exterior angle (in degrees)?
  24. 24.Can a triangle have sides of 22 cm, 12 cm and 6 cm? (a) Yes (b) No
  25. 25.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  26. 26.The two interior opposite angles of a triangle are 34° and 60°. What is the exterior angle (in degrees)?
  27. 27.In triangle ABC, angle A = 26° and angle B = 100°. What is angle C (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  29. 29.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  30. 30.In triangle ABC, angle A = 66° and angle B = 44°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  35. 35.In triangle ABC, angle A = 39° and angle B = 57°. What is angle C (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  37. 37.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)?
  38. 38.Can a triangle have sides of 21 cm, 11 cm and 7 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 22 cm, 12 cm and 8 cm? (a) Yes (b) No
  40. 40.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?

Answer key

  1. 84
  2. 123
  3. Yes
  4. 72
  5. 61
  6. Yes
  7. 17
  8. 46
  9. 72
  10. 66
  11. 40
  12. 30
  13. 67
  14. 107
  15. 35
  16. 90
  17. 98
  18. 116
  19. 17
  20. No
  21. No
  22. 40
  23. 82
  24. No
  25. 15
  26. 94
  27. 54
  28. 25
  29. 5
  30. 70
  31. 34
  32. 78
  33. 45
  34. 25
  35. 84
  36. 20
  37. 15
  38. No
  39. No
  40. 69

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