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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 636 · 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 an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  3. 3.Can a triangle have sides of 3 cm, 3 cm and 7 cm? (a) Yes (b) No
  4. 4.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 53° and angle B = 45°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 73° and angle B = 59°. What is angle C (in degrees)?
  8. 8.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  9. 9.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 37° and angle B = 83°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 76° and angle B = 74°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  17. 17.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 30° and 45°. What is the exterior angle (in degrees)?
  19. 19.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  20. 20.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  21. 21.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  22. 22.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)?
  23. 23.Can a triangle have sides of 18 cm, 6 cm and 8 cm? (a) No (b) Yes
  24. 24.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  25. 25.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  26. 26.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  28. 28.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  36. 36.Can a triangle have sides of 17 cm, 11 cm and 7 cm? (a) No (b) Yes
  37. 37.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?

Answer key

  1. 23
  2. 17
  3. No
  4. 80
  5. 21
  6. 82
  7. 48
  8. 24
  9. 42
  10. 100
  11. 36
  12. 60
  13. 58
  14. 21
  15. 30
  16. 90
  17. 64
  18. 75
  19. 33
  20. 60
  21. 3
  22. 5
  23. No
  24. 37
  25. 20
  26. 64
  27. 67
  28. 25
  29. 25
  30. 80
  31. 62
  32. 17
  33. 26
  34. 62
  35. 10
  36. Yes
  37. 73
  38. 36
  39. 15
  40. 57

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