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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 599 · 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 = 83° and angle B = 65°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 38° and angle B = 36°. What is angle C (in degrees)?
  3. 3.Can a triangle have sides of 5 cm, 4 cm and 5 cm? (a) Yes (b) No
  4. 4.Can a triangle have sides of 7 cm, 17 cm and 7 cm? (a) No (b) Yes
  5. 5.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  6. 6.Can a triangle have sides of 15 cm, 10 cm and 4 cm? (a) Yes (b) No
  7. 7.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 30° and angle B = 84°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 41° and angle B = 93°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 56° and angle B = 97°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 74° and angle B = 70°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  14. 14.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 98° and angle B = 44°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 12 cm, 9 cm and 25 cm? (a) Yes (b) No
  21. 21.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  22. 22.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  23. 23.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  25. 25.In triangle ABC, angle A = 72° and angle B = 33°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 83° and angle B = 23°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 97° and angle B = 30°. What is angle C (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 38° and angle B = 76°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 5 cm, 7 cm and 7 cm? (a) No (b) Yes
  31. 31.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  32. 32.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 52° and 71°. What is the exterior angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  35. 35.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  36. 36.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  37. 37.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  38. 38.In triangle ABC, angle A = 57° and angle B = 82°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?

Answer key

  1. 32
  2. 106
  3. Yes
  4. No
  5. 67
  6. No
  7. 46
  8. 66
  9. 46
  10. 27
  11. 100
  12. 36
  13. 90
  14. 47
  15. 72
  16. 54
  17. 72
  18. 34
  19. 38
  20. No
  21. 42
  22. 36
  23. 12
  24. 28
  25. 75
  26. 74
  27. 53
  28. 20
  29. 66
  30. Yes
  31. 54
  32. 47
  33. 123
  34. 17
  35. 25
  36. 26
  37. 15
  38. 41
  39. 71
  40. 62

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