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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 747 · 40 sums
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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 = 98° and angle B = 41°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 76° and angle B = 35°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  5. 5.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  6. 6.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  7. 7.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 3 cm, 9 cm and 8 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 89° and angle B = 58°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 51° and angle B = 61°. What is angle C (in degrees)?
  12. 12.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)?
  13. 13.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  14. 14.In triangle ABC, angle A = 100° and angle B = 44°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 33° and angle B = 27°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 33° and angle B = 47°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 8 cm, 12 cm and 7 cm? (a) No (b) Yes
  19. 19.In triangle ABC, angle A = 82° and angle B = 37°. What is angle C (in degrees)?
  20. 20.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  21. 21.In triangle ABC, angle A = 98° and angle B = 50°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 3 cm, 7 cm and 7 cm? (a) No (b) Yes
  23. 23.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 69° and 74°. What is the exterior angle (in degrees)?
  26. 26.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  29. 29.Can a triangle have sides of 12 cm, 8 cm and 10 cm? (a) Yes (b) No
  30. 30.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  32. 32.An exterior angle of a triangle is 50°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 94° and angle B = 40°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 59° and 35°. What is the exterior angle (in degrees)?
  36. 36.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 78° and 58°. What is the exterior angle (in degrees)?
  38. 38.In triangle ABC, angle A = 94° and angle B = 46°. What is angle C (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 40° and 59°. What is the exterior angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?

Answer key

  1. 41
  2. 69
  3. 25
  4. 5
  5. 72
  6. 12
  7. 27
  8. 136
  9. Yes
  10. 33
  11. 68
  12. 5
  13. 55
  14. 36
  15. 120
  16. 43
  17. 100
  18. Yes
  19. 61
  20. 12
  21. 32
  22. Yes
  23. 63
  24. 44
  25. 143
  26. 10
  27. 36
  28. 40
  29. Yes
  30. 12
  31. 24
  32. 26
  33. 37
  34. 46
  35. 94
  36. 46
  37. 136
  38. 40
  39. 99
  40. 50

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