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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 693 · 40 sums
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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 = 22° and angle B = 110°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 54° and angle B = 43°. What is angle C (in degrees)?
  3. 3.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)?
  4. 4.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  7. 7.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 8 cm, 9 cm and 11 cm? (a) Yes (b) No
  9. 9.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  11. 11.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  12. 12.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  13. 13.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)?
  14. 14.In triangle ABC, angle A = 96° and angle B = 63°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 56° and 40°. What is the exterior angle (in degrees)?
  18. 18.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)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  20. 20.In triangle ABC, angle A = 83° and angle B = 55°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 59° and angle B = 54°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 89° and angle B = 64°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 26° and angle B = 94°. What is angle C (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 40° and 75°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 82° and angle B = 44°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 32° and angle B = 32°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 76° and 66°. What is the exterior angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 33° and 73°. What is the exterior angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 96° and angle B = 58°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  40. 40.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?

Answer key

  1. 48
  2. 83
  3. 24
  4. 14
  5. 10
  6. 90
  7. 72
  8. Yes
  9. 20
  10. 63
  11. 8
  12. 77
  13. 8
  14. 21
  15. 46
  16. 15
  17. 96
  18. 5
  19. 44
  20. 42
  21. 67
  22. 27
  23. 60
  24. 25
  25. 38
  26. 39
  27. 40
  28. 115
  29. 54
  30. 54
  31. 116
  32. 44
  33. 142
  34. 106
  35. 46
  36. 26
  37. 34
  38. 61
  39. 15
  40. 48

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