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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 938 · 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 an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  2. 2.In triangle ABC, angle A = 50° and angle B = 20°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  5. 5.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)?
  6. 6.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 58° and angle B = 21°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 21° and angle B = 122°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 70° and angle B = 56°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  13. 13.In triangle ABC, angle A = 72° and angle B = 28°. What is angle C (in degrees)?
  14. 14.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  15. 15.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)?
  16. 16.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  22. 22.Can a triangle have sides of 6 cm, 18 cm and 11 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 98° and angle B = 27°. What is angle C (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.In triangle ABC, angle A = 27° and angle B = 86°. What is angle C (in degrees)?
  26. 26.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)?
  27. 27.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 100° and angle B = 53°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 22° and 58°. What is the exterior angle (in degrees)?
  30. 30.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)?
  31. 31.Can a triangle have sides of 12 cm, 12 cm and 6 cm? (a) Yes (b) No
  32. 32.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)?
  33. 33.In triangle ABC, angle A = 22° and angle B = 34°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 37° and 34°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  40. 40.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?

Answer key

  1. 27
  2. 110
  3. 52
  4. 66
  5. 12
  6. 100
  7. 101
  8. 37
  9. 100
  10. 54
  11. 59
  12. 48
  13. 80
  14. 22
  15. 12
  16. 54
  17. 80
  18. 77
  19. 28
  20. 51
  21. 18
  22. No
  23. 55
  24. 44
  25. 67
  26. 8
  27. 122
  28. 27
  29. 80
  30. 15
  31. Yes
  32. 10
  33. 124
  34. 118
  35. 90
  36. 39
  37. 71
  38. 45
  39. 25
  40. 70

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