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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 909 · 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 = 94° and angle B = 33°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 76° and angle B = 80°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 10 cm, 12 cm and 9 cm? (a) No (b) Yes
  5. 5.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  6. 6.In triangle ABC, angle A = 33° and angle B = 120°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 73° and 33°. What is the exterior angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 44° and 47°. What is the exterior angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (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.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  15. 15.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  17. 17.The two interior opposite angles of a triangle are 42° and 23°. What is the exterior angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 12 cm, 10 cm and 26 cm? (a) No (b) Yes
  21. 21.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 48° and angle B = 96°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 44° and angle B = 28°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 83° and angle B = 25°. What is angle C (in degrees)?
  25. 25.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)?
  26. 26.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  27. 27.Can a triangle have sides of 15 cm, 4 cm and 10 cm? (a) No (b) Yes
  28. 28.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  29. 29.Can a triangle have sides of 7 cm, 12 cm and 7 cm? (a) Yes (b) No
  30. 30.In triangle ABC, angle A = 69° and angle B = 71°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 39° and angle B = 47°. What is angle C (in degrees)?
  32. 32.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)?
  33. 33.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)?
  34. 34.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 41° and angle B = 43°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  38. 38.In triangle ABC, angle A = 31° and angle B = 46°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 10 cm, 15 cm and 7 cm? (a) Yes (b) No
  40. 40.The two interior opposite angles of a triangle are 72° and 58°. What is the exterior angle (in degrees)?

Answer key

  1. 53
  2. 54
  3. 24
  4. Yes
  5. 43
  6. 27
  7. 90
  8. 82
  9. 28
  10. 106
  11. 91
  12. 16
  13. 8
  14. 26
  15. 100
  16. 17
  17. 65
  18. 67
  19. 48
  20. No
  21. 70
  22. 36
  23. 108
  24. 72
  25. 24
  26. 20
  27. No
  28. 17
  29. Yes
  30. 40
  31. 94
  32. 12
  33. 15
  34. 72
  35. 53
  36. 96
  37. 35
  38. 103
  39. Yes
  40. 130

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