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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 982 · 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 smallest angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  3. 3.The two interior opposite angles of a triangle are 37° and 75°. What is the exterior angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  5. 5.Can a triangle have sides of 11 cm, 4 cm and 10 cm? (a) No (b) Yes
  6. 6.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  8. 8.In triangle ABC, angle A = 42° and angle B = 48°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 41° and angle B = 48°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 31° and angle B = 54°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 12 cm, 5 cm and 9 cm? (a) No (b) Yes
  13. 13.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  14. 14.In triangle ABC, angle A = 93° and angle B = 63°. What is angle C (in degrees)?
  15. 15.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)?
  16. 16.In triangle ABC, angle A = 26° and angle B = 96°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 23° and angle B = 118°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  21. 21.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)?
  22. 22.In triangle ABC, angle A = 37° and angle B = 113°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  26. 26.Can a triangle have sides of 2 cm, 5 cm and 4 cm? (a) No (b) Yes
  27. 27.Can a triangle have sides of 7 cm, 7 cm and 18 cm? (a) No (b) Yes
  28. 28.In triangle ABC, angle A = 65° and angle B = 20°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 5 cm, 2 cm and 3 cm? (a) Yes (b) No
  31. 31.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  34. 34.Can a triangle have sides of 5 cm, 5 cm and 15 cm? (a) Yes (b) No
  35. 35.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  36. 36.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  37. 37.In triangle ABC, angle A = 31° and angle B = 119°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  39. 39.In triangle ABC, angle A = 27° and angle B = 74°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?

Answer key

  1. 18
  2. 5
  3. 112
  4. 62
  5. Yes
  6. 48
  7. 30
  8. 90
  9. 40
  10. 91
  11. 95
  12. Yes
  13. 25
  14. 24
  15. 7
  16. 58
  17. 39
  18. 126
  19. 18
  20. 39
  21. 8
  22. 30
  23. 114
  24. 38
  25. 26
  26. Yes
  27. No
  28. 95
  29. 82
  30. No
  31. 34
  32. 90
  33. 80
  34. No
  35. 36
  36. 65
  37. 30
  38. 61
  39. 79
  40. 94

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