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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 274 · 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 3 : 5 : 7. What is the biggest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 70° and 55°. What is the exterior angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 70° and 34°. What is the exterior angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 31° and angle B = 106°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  8. 8.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)?
  9. 9.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 32° and angle B = 76°. What is angle C (in degrees)?
  11. 11.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 21° and angle B = 131°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 6 cm, 10 cm and 10 cm? (a) No (b) Yes
  16. 16.Can a triangle have sides of 16 cm, 7 cm and 6 cm? (a) No (b) Yes
  17. 17.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  18. 18.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  19. 19.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  20. 20.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)?
  21. 21.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  22. 22.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 87° and angle B = 61°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 21 cm, 9 cm and 10 cm? (a) Yes (b) No
  25. 25.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 11 cm, 3 cm and 9 cm? (a) No (b) Yes
  27. 27.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 43° and angle B = 107°. What is angle C (in degrees)?
  29. 29.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 47° and angle B = 94°. What is angle C (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 22° and 46°. What is the exterior angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 36° and angle B = 26°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 47° and angle B = 81°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 94° and angle B = 53°. What is angle C (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  40. 40.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?

Answer key

  1. 84
  2. 34
  3. 125
  4. 104
  5. 74
  6. 43
  7. 76
  8. 3
  9. 51
  10. 72
  11. 15
  12. 28
  13. 48
  14. 28
  15. Yes
  16. No
  17. 62
  18. 50
  19. 22
  20. 12
  21. 40
  22. 60
  23. 32
  24. No
  25. 59
  26. Yes
  27. 30
  28. 30
  29. 26
  30. 120
  31. 39
  32. 17
  33. 68
  34. 32
  35. 118
  36. 52
  37. 106
  38. 33
  39. 39
  40. 40

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