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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 471 · 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 a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  2. 2.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)?
  3. 3.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 5 cm, 12 cm and 15 cm? (a) Yes (b) No
  7. 7.In triangle ABC, angle A = 36° and angle B = 42°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  10. 10.Can a triangle have sides of 9 cm, 8 cm and 21 cm? (a) No (b) Yes
  11. 11.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 2 cm, 6 cm and 6 cm? (a) Yes (b) No
  13. 13.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  14. 14.In triangle ABC, angle A = 66° and angle B = 93°. What is angle C (in degrees)?
  15. 15.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  16. 16.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 5 cm, 2 cm and 11 cm? (a) No (b) Yes
  18. 18.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  19. 19.Can a triangle have sides of 11 cm, 12 cm and 3 cm? (a) No (b) Yes
  20. 20.Can a triangle have sides of 10 cm, 16 cm and 4 cm? (a) No (b) Yes
  21. 21.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 36° and angle B = 68°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 23° and 22°. What is the exterior angle (in degrees)?
  24. 24.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  25. 25.Can a triangle have sides of 6 cm, 8 cm and 14 cm? (a) No (b) Yes
  26. 26.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)?
  27. 27.In triangle ABC, angle A = 42° and angle B = 39°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  29. 29.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 55° and angle B = 90°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 86° and angle B = 41°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  36. 36.In triangle ABC, angle A = 80° and angle B = 45°. What is angle C (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  38. 38.Can a triangle have sides of 8 cm, 3 cm and 10 cm? (a) No (b) Yes
  39. 39.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?

Answer key

  1. 23
  2. 24
  3. 76
  4. 75
  5. 14
  6. Yes
  7. 102
  8. 90
  9. 36
  10. No
  11. 67
  12. Yes
  13. 13
  14. 21
  15. 6
  16. 20
  17. No
  18. 27
  19. Yes
  20. No
  21. 52
  22. 76
  23. 45
  24. 54
  25. No
  26. 15
  27. 99
  28. 49
  29. 30
  30. 16
  31. 35
  32. 47
  33. 53
  34. 12
  35. 53
  36. 55
  37. 90
  38. Yes
  39. 22
  40. 30

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