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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 48 · 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 68° and 41°. What is the exterior angle (in degrees)?
  2. 2.Can a triangle have sides of 7 cm, 3 cm and 9 cm? (a) No (b) Yes
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 53° and 43°. What is the exterior angle (in degrees)?
  5. 5.Can a triangle have sides of 4 cm, 7 cm and 8 cm? (a) No (b) Yes
  6. 6.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)?
  7. 7.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 10 cm, 20 cm and 9 cm? (a) No (b) Yes
  9. 9.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  10. 10.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  11. 11.The two interior opposite angles of a triangle are 22° and 28°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 60° and angle B = 28°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 63° and 26°. What is the exterior angle (in degrees)?
  14. 14.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 28° and 31°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 9 cm, 3 cm and 13 cm? (a) No (b) Yes
  17. 17.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 10 cm, 20 cm and 10 cm? (a) Yes (b) No
  19. 19.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 83° each. 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 a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 26° and angle B = 64°. What is angle C (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 71° and 34°. What is the exterior angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 63° and 51°. What is the exterior angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  31. 31.An exterior angle of a triangle is 146°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  34. 34.Can a triangle have sides of 5 cm, 12 cm and 22 cm? (a) Yes (b) No
  35. 35.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)?
  36. 36.Can a triangle have sides of 10 cm, 5 cm and 10 cm? (a) No (b) Yes
  37. 37.In triangle ABC, angle A = 40° and angle B = 113°. What is angle C (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  39. 39.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  40. 40.In triangle ABC, angle A = 49° and angle B = 39°. What is angle C (in degrees)?

Answer key

  1. 109
  2. Yes
  3. 90
  4. 96
  5. Yes
  6. 8
  7. 15
  8. No
  9. 17
  10. 25
  11. 50
  12. 92
  13. 89
  14. 28
  15. 59
  16. No
  17. 29
  18. No
  19. 25
  20. 14
  21. 132
  22. 31
  23. 67
  24. 20
  25. 90
  26. 105
  27. 114
  28. 40
  29. 104
  30. 31
  31. 67
  32. 48
  33. 72
  34. No
  35. 10
  36. Yes
  37. 27
  38. 17
  39. 37
  40. 92

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