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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 950 · 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 triangle ABC, angle A = 85° and angle B = 24°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 88° and angle B = 41°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 31° and angle B = 90°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  9. 9.In triangle ABC, angle A = 90° and angle B = 51°. What is angle C (in degrees)?
  10. 10.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  13. 13.Can a triangle have sides of 10 cm, 11 cm and 4 cm? (a) No (b) Yes
  14. 14.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  20. 20.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)?
  21. 21.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 12 cm, 3 cm and 8 cm? (a) No (b) Yes
  26. 26.The two interior opposite angles of a triangle are 43° and 64°. What is the exterior angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  28. 28.In triangle ABC, angle A = 70° and angle B = 71°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 5 cm, 10 cm and 11 cm? (a) Yes (b) No
  32. 32.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 18 cm, 10 cm and 12 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 35° and 45°. What is the exterior angle (in degrees)?
  36. 36.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 21° and 22°. What is the exterior angle (in degrees)?
  39. 39.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)?
  40. 40.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)?

Answer key

  1. 71
  2. 20
  3. 45
  4. 51
  5. 59
  6. 52
  7. 14
  8. 19
  9. 39
  10. 76
  11. 72
  12. 15
  13. Yes
  14. 15
  15. 70
  16. 11
  17. 25
  18. 90
  19. 26
  20. 8
  21. 28
  22. 37
  23. 20
  24. 36
  25. No
  26. 107
  27. 24
  28. 39
  29. 134
  30. 53
  31. Yes
  32. 50
  33. 66
  34. Yes
  35. 80
  36. 71
  37. 66
  38. 43
  39. 12
  40. 15

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