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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 563 · 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 = 62° and angle B = 62°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 73° and 29°. What is the exterior angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 72° and angle B = 59°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 48° and angle B = 35°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 27° and angle B = 131°. What is angle C (in degrees)?
  11. 11.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)?
  12. 12.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  13. 13.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  14. 14.Can a triangle have sides of 8 cm, 10 cm and 10 cm? (a) No (b) Yes
  15. 15.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 71° and 23°. What is the exterior angle (in degrees)?
  18. 18.In triangle ABC, angle A = 90° and angle B = 39°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 76° and angle B = 40°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 57° and angle B = 99°. What is angle C (in degrees)?
  21. 21.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  25. 25.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 49° and 78°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 26° and angle B = 67°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  32. 32.Can a triangle have sides of 10 cm, 2 cm and 10 cm? (a) Yes (b) No
  33. 33.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  36. 36.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  37. 37.Can a triangle have sides of 12 cm, 3 cm and 8 cm? (a) Yes (b) No
  38. 38.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  40. 40.Can a triangle have sides of 7 cm, 7 cm and 11 cm? (a) Yes (b) No

Answer key

  1. 56
  2. 31
  3. 45
  4. 102
  5. 45
  6. 124
  7. 49
  8. 90
  9. 97
  10. 22
  11. 24
  12. 20
  13. 52
  14. Yes
  15. 34
  16. 20
  17. 94
  18. 51
  19. 64
  20. 24
  21. 21
  22. 37
  23. 108
  24. 69
  25. 66
  26. 88
  27. 127
  28. 87
  29. 62
  30. 18
  31. 48
  32. Yes
  33. 90
  34. 36
  35. 27
  36. 34
  37. No
  38. 73
  39. 39
  40. Yes

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