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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 224 · 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 triangle ABC, angle A = 35° and angle B = 115°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 35° and 29°. What is the exterior angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  5. 5.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 48° and 53°. What is the exterior angle (in degrees)?
  9. 9.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  10. 10.Can a triangle have sides of 2 cm, 7 cm and 9 cm? (a) Yes (b) No
  11. 11.Can a triangle have sides of 9 cm, 13 cm and 7 cm? (a) Yes (b) No
  12. 12.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 47° and 47°. What is the exterior angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 22° and 20°. What is the exterior angle (in degrees)?
  17. 17.In triangle ABC, angle A = 44° and angle B = 94°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  19. 19.In triangle ABC, angle A = 78° and angle B = 47°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 3 cm, 4 cm and 7 cm? (a) No (b) Yes
  21. 21.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 50° and 51°. What is the exterior angle (in degrees)?
  24. 24.Can a triangle have sides of 14 cm, 7 cm and 7 cm? (a) No (b) Yes
  25. 25.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 70° and angle B = 45°. What is angle C (in degrees)?
  28. 28.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)?
  29. 29.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  32. 32.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)?
  33. 33.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 53° and angle B = 87°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 81° and angle B = 23°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 150°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?

Answer key

  1. 30
  2. 48
  3. 64
  4. 32
  5. 54
  6. 126
  7. 138
  8. 101
  9. 10
  10. No
  11. Yes
  12. 116
  13. 73
  14. 94
  15. 17
  16. 42
  17. 42
  18. 77
  19. 55
  20. No
  21. 45
  22. 40
  23. 101
  24. No
  25. 40
  26. 16
  27. 65
  28. 15
  29. 52
  30. 72
  31. 11
  32. 7
  33. 34
  34. 40
  35. 57
  36. 76
  37. 73
  38. 19
  39. 69
  40. 88

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