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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 586 · 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 = 29° and angle B = 124°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 96° and angle B = 34°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  6. 6.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)?
  7. 7.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 24° and angle B = 90°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  12. 12.Can a triangle have sides of 21 cm, 6 cm and 10 cm? (a) No (b) Yes
  13. 13.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 74° and 24°. What is the exterior angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 31° and 43°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 12 cm, 10 cm and 2 cm? (a) No (b) Yes
  27. 27.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 2 cm, 3 cm and 2 cm? (a) No (b) Yes
  29. 29.Can a triangle have sides of 10 cm, 10 cm and 5 cm? (a) No (b) Yes
  30. 30.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  34. 34.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 22° and angle B = 32°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 27° and 45°. What is the exterior angle (in degrees)?
  37. 37.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 85° and angle B = 66°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 35° and angle B = 69°. What is angle C (in degrees)?

Answer key

  1. 27
  2. 50
  3. 34
  4. 70
  5. 30
  6. 15
  7. 51
  8. 26
  9. 66
  10. 32
  11. 30
  12. No
  13. 14
  14. 15
  15. 98
  16. 80
  17. 62
  18. 30
  19. 75
  20. 33
  21. 94
  22. 112
  23. 74
  24. 40
  25. 54
  26. No
  27. 61
  28. Yes
  29. Yes
  30. 35
  31. 90
  32. 63
  33. 17
  34. 72
  35. 126
  36. 72
  37. 20
  38. 29
  39. 18
  40. 76

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