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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 419 · 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.

NameDateTime takenScore ___ / 40
  1. 1.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  2. 2.Can a triangle have sides of 19 cm, 7 cm and 9 cm? (a) Yes (b) No
  3. 3.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  4. 4.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  5. 5.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  12. 12.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  13. 13.Can a triangle have sides of 5 cm, 12 cm and 12 cm? (a) No (b) Yes
  14. 14.In triangle ABC, angle A = 36° and angle B = 43°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 80° and angle B = 75°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 10 cm, 10 cm and 8 cm? (a) No (b) Yes
  17. 17.The two interior opposite angles of a triangle are 52° and 28°. What is the exterior angle (in degrees)?
  18. 18.In triangle ABC, angle A = 47° and angle B = 44°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 6 cm, 4 cm and 11 cm? (a) Yes (b) No
  20. 20.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 43° and angle B = 46°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 36° and angle B = 54°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 78° and angle B = 32°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 4 cm, 8 cm and 4 cm? (a) No (b) Yes
  28. 28.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)?
  29. 29.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  30. 30.Can a triangle have sides of 10 cm, 10 cm and 24 cm? (a) Yes (b) No
  31. 31.Can a triangle have sides of 9 cm, 12 cm and 13 cm? (a) Yes (b) No
  32. 32.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 97° and angle B = 22°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 20 cm, 10 cm and 10 cm? (a) No (b) Yes
  35. 35.In triangle ABC, angle A = 74° and angle B = 74°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 65° and angle B = 39°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  39. 39.Can a triangle have sides of 5 cm, 14 cm and 5 cm? (a) Yes (b) No
  40. 40.In triangle ABC, angle A = 94° and angle B = 65°. What is angle C (in degrees)?

Answer key

  1. 72
  2. No
  3. 64
  4. 36
  5. 11
  6. 28
  7. 36
  8. 90
  9. 14
  10. 36
  11. 10
  12. 70
  13. Yes
  14. 101
  15. 25
  16. Yes
  17. 80
  18. 89
  19. No
  20. 72
  21. 91
  22. 65
  23. 90
  24. 42
  25. 10
  26. 70
  27. No
  28. 7
  29. 90
  30. No
  31. Yes
  32. 70
  33. 61
  34. No
  35. 32
  36. 76
  37. 34
  38. 18
  39. No
  40. 21

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