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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 519 · 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 two interior opposite angles of a triangle are 25° and 32°. What is the exterior angle (in degrees)?
  2. 2.Can a triangle have sides of 10 cm, 8 cm and 21 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 90° and angle B = 29°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 66° and angle B = 64°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  6. 6.In triangle ABC, angle A = 31° and angle B = 104°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (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.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 19 cm and 10 cm? (a) Yes (b) No
  11. 11.Can a triangle have sides of 12 cm, 5 cm and 7 cm? (a) Yes (b) No
  12. 12.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  13. 13.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)?
  14. 14.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  15. 15.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  17. 17.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  18. 18.The two interior opposite angles of a triangle are 38° and 30°. What is the exterior angle (in degrees)?
  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.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)?
  21. 21.Can a triangle have sides of 11 cm, 2 cm and 10 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  24. 24.Can a triangle have sides of 2 cm, 6 cm and 6 cm? (a) Yes (b) No
  25. 25.In triangle ABC, angle A = 35° and angle B = 74°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 7 cm, 3 cm and 7 cm? (a) No (b) Yes
  27. 27.Can a triangle have sides of 6 cm, 16 cm and 6 cm? (a) Yes (b) No
  28. 28.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 79° and angle B = 80°. What is angle C (in degrees)?
  31. 31.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  32. 32.The two interior opposite angles of a triangle are 44° and 36°. What is the exterior angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 6 cm and 3 cm? (a) Yes (b) No
  35. 35.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  36. 36.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)?
  37. 37.Can a triangle have sides of 2 cm, 4 cm and 10 cm? (a) No (b) Yes
  38. 38.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  39. 39.Can a triangle have sides of 3 cm, 2 cm and 3 cm? (a) No (b) Yes
  40. 40.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?

Answer key

  1. 57
  2. No
  3. 61
  4. 50
  5. 20
  6. 45
  7. 37
  8. 90
  9. 32
  10. Yes
  11. No
  12. 48
  13. 8
  14. 96
  15. 69
  16. 34
  17. 18
  18. 68
  19. 25
  20. 15
  21. Yes
  22. 72
  23. 120
  24. Yes
  25. 71
  26. Yes
  27. No
  28. 100
  29. 72
  30. 21
  31. 3
  32. 80
  33. 46
  34. No
  35. 51
  36. 15
  37. No
  38. 20
  39. Yes
  40. 48

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