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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 595 · 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.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 31° and angle B = 91°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  7. 7.In triangle ABC, angle A = 88° and angle B = 22°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  9. 9.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 64° and angle B = 52°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 22° and angle B = 27°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 65° and angle B = 72°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 73° and 37°. What is the exterior angle (in degrees)?
  14. 14.Can a triangle have sides of 2 cm, 2 cm and 2 cm? (a) No (b) Yes
  15. 15.In triangle ABC, angle A = 98° and angle B = 60°. What is angle C (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  17. 17.In triangle ABC, angle A = 51° and angle B = 64°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 79° and 65°. What is the exterior angle (in degrees)?
  19. 19.Can a triangle have sides of 4 cm, 2 cm and 3 cm? (a) Yes (b) No
  20. 20.Can a triangle have sides of 3 cm, 3 cm and 5 cm? (a) No (b) Yes
  21. 21.In triangle ABC, angle A = 20° and angle B = 23°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 4 cm, 9 cm and 9 cm? (a) Yes (b) No
  24. 24.Can a triangle have sides of 11 cm, 10 cm and 10 cm? (a) No (b) Yes
  25. 25.The two interior opposite angles of a triangle are 59° and 44°. What is the exterior angle (in degrees)?
  26. 26.Can a triangle have sides of 9 cm, 9 cm and 18 cm? (a) No (b) Yes
  27. 27.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 62° and 28°. What is the exterior angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  31. 31.In triangle ABC, angle A = 59° and angle B = 36°. What is angle C (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 61° and 21°. What is the exterior angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  34. 34.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 74° and 61°. What is the exterior angle (in degrees)?
  36. 36.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  37. 37.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  38. 38.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  39. 39.In triangle ABC, angle A = 63° and angle B = 28°. What is angle C (in degrees)?
  40. 40.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?

Answer key

  1. 18
  2. 44
  3. 100
  4. 58
  5. 55
  6. 49
  7. 70
  8. 45
  9. 30
  10. 64
  11. 131
  12. 43
  13. 110
  14. Yes
  15. 22
  16. 26
  17. 65
  18. 144
  19. Yes
  20. Yes
  21. 137
  22. 67
  23. Yes
  24. Yes
  25. 103
  26. No
  27. 77
  28. 27
  29. 90
  30. 62
  31. 85
  32. 82
  33. 34
  34. 26
  35. 135
  36. 4
  37. 60
  38. 5
  39. 89
  40. 75

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