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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 129 · 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.

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  1. 1.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 42° and angle B = 23°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 6 cm, 6 cm and 7 cm? (a) No (b) Yes
  7. 7.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 64° and angle B = 87°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 26° and angle B = 131°. What is angle C (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  13. 13.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  14. 14.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  15. 15.Can a triangle have sides of 6 cm, 3 cm and 8 cm? (a) No (b) Yes
  16. 16.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  17. 17.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)?
  18. 18.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 34° and 77°. What is the exterior angle (in degrees)?
  20. 20.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  23. 23.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 94° and angle B = 41°. What is angle C (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  27. 27.In triangle ABC, angle A = 59° and angle B = 26°. What is angle C (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 43° and angle B = 90°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  31. 31.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)?
  32. 32.In triangle ABC, angle A = 30° and angle B = 107°. What is angle C (in degrees)?
  33. 33.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)?
  34. 34.In triangle ABC, angle A = 67° and angle B = 37°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 16 cm, 6 cm and 9 cm? (a) Yes (b) No
  36. 36.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)?
  37. 37.The two interior opposite angles of a triangle are 68° and 36°. What is the exterior angle (in degrees)?
  38. 38.In triangle ABC, angle A = 27° and angle B = 56°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 41° and angle B = 22°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?

Answer key

  1. 52
  2. 115
  3. 31
  4. 80
  5. 48
  6. Yes
  7. 104
  8. 29
  9. 20
  10. 36
  11. 23
  12. 40
  13. 6
  14. 17
  15. Yes
  16. 36
  17. 5
  18. 116
  19. 111
  20. 74
  21. 77
  22. 69
  23. 61
  24. 45
  25. 38
  26. 25
  27. 95
  28. 71
  29. 47
  30. 28
  31. 12
  32. 43
  33. 8
  34. 76
  35. No
  36. 15
  37. 104
  38. 97
  39. 117
  40. 50

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