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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 629 · 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.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  2. 2.Can a triangle have sides of 4 cm, 8 cm and 8 cm? (a) No (b) Yes
  3. 3.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  5. 5.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)?
  6. 6.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 8 cm, 8 cm and 8 cm? (a) Yes (b) No
  9. 9.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  10. 10.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  11. 11.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 73° and angle B = 33°. What is angle C (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  18. 18.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 24° and 69°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 38° and angle B = 106°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 54° and angle B = 22°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 48° and angle B = 46°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 146°. What is each of the other two angles (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 27° and 59°. What is the exterior angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 6 cm, 12 cm and 20 cm? (a) No (b) Yes
  31. 31.In triangle ABC, angle A = 45° and angle B = 41°. What is angle C (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 29° and 70°. What is the exterior angle (in degrees)?
  33. 33.Can a triangle have sides of 6 cm, 5 cm and 7 cm? (a) Yes (b) No
  34. 34.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 30° and angle B = 38°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?

Answer key

  1. 55
  2. Yes
  3. 33
  4. 14
  5. 15
  6. 52
  7. 11
  8. Yes
  9. 8
  10. 68
  11. 28
  12. 72
  13. 82
  14. 62
  15. 100
  16. 74
  17. 60
  18. 24
  19. 120
  20. 93
  21. 36
  22. 104
  23. 80
  24. 86
  25. 20
  26. 130
  27. 17
  28. 86
  29. 50
  30. No
  31. 94
  32. 99
  33. Yes
  34. 32
  35. 78
  36. 112
  37. 29
  38. 90
  39. 54
  40. 48

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