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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 180 · 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.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 23 cm, 12 cm and 6 cm? (a) Yes (b) No
  5. 5.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)?
  6. 6.Can a triangle have sides of 12 cm, 4 cm and 5 cm? (a) Yes (b) No
  7. 7.In triangle ABC, angle A = 86° and angle B = 27°. What is angle C (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  9. 9.In triangle ABC, angle A = 49° and angle B = 21°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 23° and angle B = 134°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 27° and angle B = 107°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  15. 15.Can a triangle have sides of 17 cm, 5 cm and 9 cm? (a) Yes (b) No
  16. 16.Can a triangle have sides of 9 cm, 19 cm and 9 cm? (a) Yes (b) No
  17. 17.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 7 cm, 4 cm and 7 cm? (a) Yes (b) No
  19. 19.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  20. 20.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 50° and angle B = 24°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  25. 25.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  26. 26.Can a triangle have sides of 16 cm, 2 cm and 9 cm? (a) Yes (b) No
  27. 27.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 89° and angle B = 22°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 48° and angle B = 60°. What is angle C (in degrees)?
  34. 34.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  35. 35.Can a triangle have sides of 9 cm, 2 cm and 10 cm? (a) Yes (b) No
  36. 36.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)?
  37. 37.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  38. 38.Can a triangle have sides of 6 cm, 2 cm and 7 cm? (a) No (b) Yes
  39. 39.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  40. 40.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?

Answer key

  1. 90
  2. 45
  3. 58
  4. No
  5. 15
  6. No
  7. 67
  8. 10
  9. 110
  10. 23
  11. 32
  12. 46
  13. 140
  14. 39
  15. No
  16. No
  17. 80
  18. Yes
  19. 25
  20. 60
  21. 132
  22. 106
  23. 46
  24. 30
  25. 44
  26. No
  27. 63
  28. 100
  29. 79
  30. 29
  31. 69
  32. 104
  33. 72
  34. 24
  35. Yes
  36. 15
  37. 5
  38. Yes
  39. 17
  40. 21

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