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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 441 · 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.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  2. 2.Can a triangle have sides of 12 cm, 2 cm and 9 cm? (a) Yes (b) No
  3. 3.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  4. 4.In triangle ABC, angle A = 39° and angle B = 32°. What is angle C (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 38° and angle B = 76°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  12. 12.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  13. 13.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 10 cm, 14 cm and 8 cm? (a) No (b) Yes
  16. 16.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 44° and angle B = 31°. What is angle C (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  19. 19.The two interior opposite angles of a triangle are 39° and 57°. What is the exterior angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 30° and 31°. What is the exterior angle (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 12 cm and 20 cm? (a) No (b) Yes
  22. 22.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  23. 23.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)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  25. 25.Can a triangle have sides of 3 cm, 2 cm and 2 cm? (a) No (b) Yes
  26. 26.Can a triangle have sides of 3 cm, 8 cm and 7 cm? (a) Yes (b) No
  27. 27.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  28. 28.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 26° and angle B = 62°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 21° and angle B = 49°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 99° and angle B = 34°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 30° and angle B = 127°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 4 cm, 11 cm and 8 cm? (a) No (b) Yes
  37. 37.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  38. 38.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  39. 39.Can a triangle have sides of 10 cm, 9 cm and 11 cm? (a) Yes (b) No
  40. 40.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?

Answer key

  1. 20
  2. No
  3. 100
  4. 109
  5. 72
  6. 66
  7. 22
  8. 40
  9. 78
  10. 130
  11. 17
  12. 25
  13. 18
  14. 56
  15. Yes
  16. 22
  17. 105
  18. 5
  19. 96
  20. 61
  21. Yes
  22. 41
  23. 5
  24. 54
  25. Yes
  26. Yes
  27. 25
  28. 54
  29. 92
  30. 110
  31. 20
  32. 10
  33. 54
  34. 47
  35. 23
  36. Yes
  37. 17
  38. 75
  39. Yes
  40. 4

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