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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 107 · 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 12 cm, 4 cm and 6 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 7 cm, 4 cm and 8 cm? (a) No (b) Yes
  4. 4.The two interior opposite angles of a triangle are 22° and 59°. What is the exterior angle (in degrees)?
  5. 5.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  6. 6.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)?
  7. 7.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  8. 8.In triangle ABC, angle A = 85° and angle B = 51°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 24° and 40°. What is the exterior angle (in degrees)?
  12. 12.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  14. 14.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  17. 17.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  21. 21.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  22. 22.In triangle ABC, angle A = 35° and angle B = 113°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  25. 25.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 85° and angle B = 50°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  28. 28.Can a triangle have sides of 6 cm, 10 cm and 20 cm? (a) Yes (b) No
  29. 29.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 61° and 58°. What is the exterior angle (in degrees)?
  31. 31.In triangle ABC, angle A = 57° and angle B = 66°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 23° and 30°. What is the exterior angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  35. 35.Can a triangle have sides of 17 cm, 7 cm and 6 cm? (a) No (b) Yes
  36. 36.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 46° and 57°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?

Answer key

  1. No
  2. 44
  3. Yes
  4. 81
  5. 15
  6. 24
  7. 36
  8. 44
  9. 118
  10. 75
  11. 64
  12. 76
  13. 90
  14. 38
  15. 14
  16. 64
  17. 72
  18. 36
  19. 51
  20. 17
  21. 3
  22. 32
  23. 10
  24. 17
  25. 30
  26. 45
  27. 72
  28. No
  29. 41
  30. 119
  31. 57
  32. 90
  33. 53
  34. 100
  35. No
  36. 86
  37. 103
  38. 20
  39. 63
  40. 73

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