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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 887 · 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 angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 91° and angle B = 21°. What is angle C (in degrees)?
  4. 4.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)?
  5. 5.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 24° and angle B = 59°. What is angle C (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  8. 8.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 80° and angle B = 51°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 7 cm, 11 cm and 6 cm? (a) Yes (b) No
  12. 12.Can a triangle have sides of 2 cm, 12 cm and 12 cm? (a) No (b) Yes
  13. 13.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  15. 15.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 99° and angle B = 34°. What is angle C (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  20. 20.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 50° and 47°. What is the exterior angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  26. 26.The two interior opposite angles of a triangle are 52° and 49°. What is the exterior angle (in degrees)?
  27. 27.In triangle ABC, angle A = 70° and angle B = 76°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 64° and angle B = 95°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  33. 33.Can a triangle have sides of 9 cm, 2 cm and 9 cm? (a) Yes (b) No
  34. 34.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 77° and angle B = 77°. What is angle C (in degrees)?

Answer key

  1. 90
  2. 72
  3. 68
  4. 7
  5. 29
  6. 97
  7. 15
  8. 22
  9. 40
  10. 49
  11. Yes
  12. Yes
  13. 74
  14. 70
  15. 62
  16. 47
  17. 25
  18. 12
  19. 30
  20. 41
  21. 97
  22. 18
  23. 24
  24. 57
  25. 5
  26. 101
  27. 34
  28. 55
  29. 76
  30. 26
  31. 21
  32. 41
  33. Yes
  34. 48
  35. 17
  36. 67
  37. 48
  38. 20
  39. 64
  40. 26

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