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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 756 · 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.The two interior opposite angles of a triangle are 74° and 43°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 91° and angle B = 44°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  5. 5.Can a triangle have sides of 8 cm, 2 cm and 9 cm? (a) No (b) Yes
  6. 6.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  7. 7.In triangle ABC, angle A = 69° and angle B = 25°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 86° and angle B = 31°. What is angle C (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 72° and 55°. What is the exterior angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 23° and 52°. What is the exterior angle (in degrees)?
  12. 12.Can a triangle have sides of 12 cm, 2 cm and 11 cm? (a) No (b) Yes
  13. 13.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  14. 14.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)?
  15. 15.The two interior opposite angles of a triangle are 52° and 54°. What is the exterior angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  17. 17.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  18. 18.In triangle ABC, angle A = 60° and angle B = 34°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 20° and angle B = 49°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  21. 21.In triangle ABC, angle A = 43° and angle B = 39°. What is angle C (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  23. 23.In triangle ABC, angle A = 40° and angle B = 22°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  25. 25.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  26. 26.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  27. 27.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  30. 30.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  33. 33.Can a triangle have sides of 9 cm, 12 cm and 26 cm? (a) Yes (b) No
  34. 34.In triangle ABC, angle A = 67° and angle B = 35°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  38. 38.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)?
  39. 39.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 54° and 68°. What is the exterior angle (in degrees)?

Answer key

  1. 117
  2. 67
  3. 45
  4. 57
  5. Yes
  6. 25
  7. 86
  8. 63
  9. 127
  10. 55
  11. 75
  12. Yes
  13. 59
  14. 15
  15. 106
  16. 62
  17. 15
  18. 86
  19. 111
  20. 25
  21. 98
  22. 17
  23. 118
  24. 45
  25. 28
  26. 24
  27. 79
  28. 45
  29. 16
  30. 84
  31. 10
  32. 75
  33. No
  34. 78
  35. 18
  36. 40
  37. 72
  38. 12
  39. 45
  40. 122

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