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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 128 · 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 70° and 44°. What is the exterior angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 43° and angle B = 75°. What is angle C (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 44° and 71°. What is the exterior angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  7. 7.Can a triangle have sides of 12 cm, 8 cm and 20 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 27° and angle B = 69°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 59° and angle B = 61°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 3 cm, 10 cm and 13 cm? (a) No (b) Yes
  14. 14.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  15. 15.Can a triangle have sides of 8 cm, 4 cm and 9 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 72° and angle B = 78°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  19. 19.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  20. 20.Can a triangle have sides of 12 cm, 2 cm and 10 cm? (a) No (b) Yes
  21. 21.Can a triangle have sides of 22 cm, 8 cm and 9 cm? (a) No (b) Yes
  22. 22.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 54° and angle B = 95°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 11 cm, 17 cm and 4 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 30° and angle B = 29°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 12 cm, 8 cm and 25 cm? (a) Yes (b) No
  28. 28.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  29. 29.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)?
  30. 30.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 71° and 23°. What is the exterior angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  33. 33.Can a triangle have sides of 11 cm, 4 cm and 4 cm? (a) Yes (b) No
  34. 34.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  35. 35.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 62° and angle B = 26°. What is angle C (in degrees)?
  37. 37.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  38. 38.In triangle ABC, angle A = 85° and angle B = 24°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 73° and angle B = 83°. What is angle C (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 52° and 74°. What is the exterior angle (in degrees)?

Answer key

  1. 114
  2. 30
  3. 73
  4. 62
  5. 115
  6. 50
  7. No
  8. 102
  9. 100
  10. 84
  11. 72
  12. 60
  13. No
  14. 32
  15. Yes
  16. 66
  17. 30
  18. 49
  19. 46
  20. No
  21. No
  22. 10
  23. 90
  24. 31
  25. No
  26. 121
  27. No
  28. 25
  29. 7
  30. 94
  31. 94
  32. 36
  33. No
  34. 12
  35. 84
  36. 92
  37. 18
  38. 71
  39. 24
  40. 126

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