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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 47 · 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.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 67° and angle B = 47°. What is angle C (in degrees)?
  3. 3.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)?
  4. 4.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 65° and angle B = 35°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 15 cm, 4 cm and 6 cm? (a) No (b) Yes
  8. 8.Can a triangle have sides of 10 cm, 3 cm and 11 cm? (a) No (b) Yes
  9. 9.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 10 cm, 5 cm and 9 cm? (a) Yes (b) No
  12. 12.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  13. 13.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)?
  14. 14.Can a triangle have sides of 8 cm, 3 cm and 12 cm? (a) No (b) Yes
  15. 15.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 17 cm, 12 cm and 9 cm? (a) No (b) Yes
  17. 17.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 45° and angle B = 76°. What is angle C (in degrees)?
  19. 19.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  20. 20.Can a triangle have sides of 7 cm, 22 cm and 11 cm? (a) Yes (b) No
  21. 21.The two interior opposite angles of a triangle are 59° and 20°. What is the exterior angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 21° and 79°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 92° and angle B = 58°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 40° and angle B = 88°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 7 cm, 9 cm and 11 cm? (a) No (b) Yes
  28. 28.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  29. 29.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  30. 30.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  32. 32.In triangle ABC, angle A = 76° and angle B = 53°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  34. 34.In triangle ABC, angle A = 45° and angle B = 44°. What is angle C (in degrees)?
  35. 35.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)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  37. 37.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  38. 38.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  39. 39.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?

Answer key

  1. 90
  2. 66
  3. 15
  4. 24
  5. 80
  6. 18
  7. No
  8. Yes
  9. 48
  10. 28
  11. Yes
  12. 7
  13. 12
  14. No
  15. 47
  16. Yes
  17. 10
  18. 59
  19. 55
  20. No
  21. 79
  22. 73
  23. 100
  24. 30
  25. 75
  26. 52
  27. Yes
  28. 10
  29. 61
  30. 48
  31. 39
  32. 51
  33. 25
  34. 91
  35. 10
  36. 41
  37. 37
  38. 57
  39. 73
  40. 68

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