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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 566 · 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 = 79° and angle B = 59°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 26° and 65°. What is the exterior angle (in degrees)?
  3. 3.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)?
  4. 4.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 52° and angle B = 57°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 3 cm, 20 cm and 12 cm? (a) Yes (b) No
  7. 7.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 94° and angle B = 65°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 60° and 47°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 44° and angle B = 62°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 58° and 74°. What is the exterior angle (in degrees)?
  14. 14.In triangle ABC, angle A = 80° and angle B = 60°. What is angle C (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  16. 16.In triangle ABC, angle A = 83° and angle B = 20°. What is angle C (in degrees)?
  17. 17.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  18. 18.Can a triangle have sides of 6 cm, 10 cm and 6 cm? (a) No (b) Yes
  19. 19.The two interior opposite angles of a triangle are 30° and 79°. What is the exterior angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 60° and 35°. What is the exterior angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  23. 23.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  24. 24.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  26. 26.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)?
  27. 27.Can a triangle have sides of 9 cm, 14 cm and 11 cm? (a) No (b) Yes
  28. 28.The two interior opposite angles of a triangle are 52° and 74°. What is the exterior angle (in degrees)?
  29. 29.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)?
  30. 30.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 40° and angle B = 80°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 4 cm, 9 cm and 5 cm? (a) No (b) Yes
  36. 36.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  37. 37.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  38. 38.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  39. 39.The two interior opposite angles of a triangle are 27° and 39°. What is the exterior angle (in degrees)?
  40. 40.Can a triangle have sides of 5 cm, 8 cm and 3 cm? (a) Yes (b) No

Answer key

  1. 42
  2. 91
  3. 8
  4. 5
  5. 71
  6. No
  7. 100
  8. 38
  9. 100
  10. 21
  11. 107
  12. 74
  13. 132
  14. 40
  15. 29
  16. 77
  17. 54
  18. Yes
  19. 109
  20. 95
  21. 36
  22. 17
  23. 15
  24. 45
  25. 75
  26. 4
  27. Yes
  28. 126
  29. 24
  30. 37
  31. 60
  32. 30
  33. 74
  34. 49
  35. No
  36. 20
  37. 15
  38. 20
  39. 66
  40. No

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