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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 36 · 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 2 : 2 : 5. What is the biggest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  4. 4.Can a triangle have sides of 7 cm, 6 cm and 2 cm? (a) No (b) Yes
  5. 5.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  6. 6.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  7. 7.In triangle ABC, angle A = 62° and angle B = 70°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 7 cm, 14 cm and 7 cm? (a) No (b) Yes
  9. 9.Can a triangle have sides of 6 cm, 4 cm and 3 cm? (a) Yes (b) No
  10. 10.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  11. 11.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  12. 12.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  13. 13.In triangle ABC, angle A = 62° and angle B = 88°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 46° and angle B = 70°. What is angle C (in degrees)?
  16. 16.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)?
  17. 17.In triangle ABC, angle A = 26° and angle B = 35°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 33° and angle B = 50°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 2 cm, 3 cm and 7 cm? (a) No (b) Yes
  24. 24.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)?
  25. 25.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 47° and angle B = 36°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 97° and angle B = 54°. What is angle C (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 95° and angle B = 44°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 5 cm, 2 cm and 5 cm? (a) No (b) Yes
  31. 31.Can a triangle have sides of 9 cm, 2 cm and 9 cm? (a) No (b) Yes
  32. 32.The two interior opposite angles of a triangle are 36° and 20°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 32° and angle B = 43°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 17 cm, 10 cm and 3 cm? (a) Yes (b) No
  35. 35.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)?
  36. 36.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 20° and angle B = 39°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 37° and 25°. What is the exterior angle (in degrees)?

Answer key

  1. 100
  2. 25
  3. 28
  4. Yes
  5. 20
  6. 55
  7. 48
  8. No
  9. Yes
  10. 90
  11. 27
  12. 36
  13. 30
  14. 72
  15. 64
  16. 15
  17. 119
  18. 34
  19. 55
  20. 97
  21. 36
  22. 34
  23. No
  24. 3
  25. 46
  26. 97
  27. 29
  28. 49
  29. 41
  30. Yes
  31. Yes
  32. 56
  33. 105
  34. No
  35. 7
  36. 45
  37. 63
  38. 121
  39. 66
  40. 62

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