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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 30 · 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 angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 12 cm, 3 cm and 13 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  9. 9.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)?
  10. 10.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 53° and angle B = 33°. What is angle C (in degrees)?
  16. 16.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)?
  17. 17.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 55° and 44°. What is the exterior angle (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 11 cm and 24 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 42° and angle B = 24°. What is angle C (in degrees)?
  23. 23.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)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 26° and angle B = 60°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 1 cm and 10 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 31° and angle B = 61°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 10 cm, 7 cm and 9 cm? (a) Yes (b) No
  30. 30.In triangle ABC, angle A = 95° and angle B = 33°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 56° and 36°. What is the exterior angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 54° and 37°. What is the exterior angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 42° and angle B = 91°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?

Answer key

  1. 36
  2. 36
  3. 45
  4. 11
  5. Yes
  6. 18
  7. 40
  8. 73
  9. 24
  10. 35
  11. 62
  12. 49
  13. 20
  14. 54
  15. 94
  16. 12
  17. 36
  18. 27
  19. 128
  20. 99
  21. No
  22. 114
  23. 8
  24. 72
  25. 94
  26. 50
  27. Yes
  28. 88
  29. Yes
  30. 52
  31. 20
  32. 50
  33. 92
  34. 91
  35. 49
  36. 36
  37. 100
  38. 47
  39. 63
  40. 25

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