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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 21 · 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.Can a triangle have sides of 3 cm, 16 cm and 9 cm? (a) No (b) Yes
  2. 2.Can a triangle have sides of 24 cm, 10 cm and 10 cm? (a) No (b) Yes
  3. 3.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 59° and angle B = 33°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 92° and angle B = 37°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  8. 8.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  10. 10.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  11. 11.In triangle ABC, angle A = 96° and angle B = 35°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  17. 17.Can a triangle have sides of 16 cm, 8 cm and 9 cm? (a) Yes (b) No
  18. 18.The two interior opposite angles of a triangle are 47° and 48°. What is the exterior angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  20. 20.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)?
  21. 21.In triangle ABC, angle A = 36° and angle B = 81°. What is angle C (in degrees)?
  22. 22.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  23. 23.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 63° and angle B = 28°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 83° and angle B = 74°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  28. 28.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 6 cm, 14 cm and 3 cm? (a) Yes (b) No
  30. 30.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  32. 32.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)?
  33. 33.The two interior opposite angles of a triangle are 51° and 53°. What is the exterior angle (in degrees)?
  34. 34.Can a triangle have sides of 14 cm, 7 cm and 5 cm? (a) Yes (b) No
  35. 35.In triangle ABC, angle A = 63° and angle B = 80°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 7 cm, 19 cm and 8 cm? (a) No (b) Yes
  37. 37.Can a triangle have sides of 11 cm, 6 cm and 6 cm? (a) Yes (b) No
  38. 38.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)?
  39. 39.Can a triangle have sides of 4 cm, 9 cm and 3 cm? (a) Yes (b) No
  40. 40.The two interior opposite angles of a triangle are 79° and 46°. What is the exterior angle (in degrees)?

Answer key

  1. No
  2. No
  3. 41
  4. 70
  5. 88
  6. 51
  7. 33
  8. 54
  9. 30
  10. 31
  11. 49
  12. 134
  13. 30
  14. 14
  15. 50
  16. 90
  17. Yes
  18. 95
  19. 15
  20. 36
  21. 63
  22. 8
  23. 25
  24. 89
  25. 23
  26. 36
  27. 20
  28. 21
  29. No
  30. 54
  31. 32
  32. 12
  33. 104
  34. No
  35. 37
  36. No
  37. Yes
  38. 10
  39. No
  40. 125

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