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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 711 · 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 = 93° and angle B = 37°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 33° and angle B = 57°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  5. 5.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  6. 6.In triangle ABC, angle A = 53° and angle B = 38°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  11. 11.An exterior angle of a triangle is 154°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  13. 13.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 62° and angle B = 87°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 41° and angle B = 40°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 60° and angle B = 74°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 4 cm, 8 cm and 2 cm? (a) Yes (b) No
  20. 20.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  24. 24.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  25. 25.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  26. 26.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 39° and 73°. What is the exterior angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 22° and 55°. What is the exterior angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 74° and 68°. What is the exterior angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  33. 33.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)?
  34. 34.The two interior opposite angles of a triangle are 26° and 46°. What is the exterior angle (in degrees)?
  35. 35.Can a triangle have sides of 9 cm, 12 cm and 22 cm? (a) Yes (b) No
  36. 36.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  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.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?

Answer key

  1. 50
  2. 90
  3. 41
  4. 17
  5. 32
  6. 89
  7. 84
  8. 18
  9. 25
  10. 90
  11. 76
  12. 30
  13. 71
  14. 110
  15. 31
  16. 16
  17. 99
  18. 46
  19. No
  20. 32
  21. 63
  22. 15
  23. 14
  24. 24
  25. 54
  26. 15
  27. 32
  28. 112
  29. 61
  30. 77
  31. 142
  32. 44
  33. 8
  34. 72
  35. No
  36. 46
  37. 15
  38. 74
  39. 46
  40. 98

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