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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 675 · 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 21 cm, 12 cm and 6 cm? (a) Yes (b) No
  2. 2.The two interior opposite angles of a triangle are 80° and 43°. What is the exterior angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  5. 5.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  6. 6.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  8. 8.In triangle ABC, angle A = 25° and angle B = 35°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  11. 11.Can a triangle have sides of 5 cm, 3 cm and 5 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 88° and angle B = 34°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 35° and angle B = 114°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 45° and angle B = 114°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 45° and angle B = 55°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 35° and 40°. What is the exterior angle (in degrees)?
  21. 21.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  22. 22.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  25. 25.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)?
  26. 26.The two interior opposite angles of a triangle are 58° and 69°. What is the exterior angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 38° and angle B = 41°. What is angle C (in degrees)?
  29. 29.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  30. 30.Can a triangle have sides of 10 cm, 22 cm and 10 cm? (a) Yes (b) No
  31. 31.In triangle ABC, angle A = 90° and angle B = 65°. What is angle C (in degrees)?
  32. 32.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  33. 33.In triangle ABC, angle A = 81° and angle B = 24°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 16 cm, 10 cm and 6 cm? (a) Yes (b) No
  40. 40.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?

Answer key

  1. No
  2. 123
  3. 18
  4. 51
  5. 12
  6. 90
  7. 48
  8. 120
  9. 32
  10. 45
  11. Yes
  12. 58
  13. 31
  14. 21
  15. 104
  16. 46
  17. 80
  18. 80
  19. 31
  20. 75
  21. 5
  22. 76
  23. 22
  24. 26
  25. 15
  26. 127
  27. 38
  28. 101
  29. 64
  30. No
  31. 25
  32. 4
  33. 75
  34. 71
  35. 112
  36. 69
  37. 50
  38. 76
  39. No
  40. 72

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