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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 342 · 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 shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  2. 2.In triangle ABC, angle A = 68° and angle B = 25°. What is angle C (in degrees)?
  3. 3.Can a triangle have sides of 22 cm, 8 cm and 11 cm? (a) No (b) Yes
  4. 4.In triangle ABC, angle A = 75° and angle B = 26°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 76° and angle B = 77°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 42° and angle B = 100°. What is angle C (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 41° and 65°. What is the exterior angle (in degrees)?
  9. 9.In triangle ABC, angle A = 70° and angle B = 70°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 7 cm, 12 cm and 8 cm? (a) No (b) Yes
  11. 11.Can a triangle have sides of 8 cm, 4 cm and 17 cm? (a) No (b) Yes
  12. 12.The two interior opposite angles of a triangle are 50° and 24°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  14. 14.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  16. 16.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 66° and 51°. What is the exterior angle (in degrees)?
  18. 18.In triangle ABC, angle A = 74° and angle B = 20°. What is angle C (in degrees)?
  19. 19.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)?
  20. 20.The two interior opposite angles of a triangle are 60° and 41°. What is the exterior angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  23. 23.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  25. 25.Can a triangle have sides of 12 cm, 21 cm and 8 cm? (a) No (b) Yes
  26. 26.Can a triangle have sides of 6 cm, 4 cm and 3 cm? (a) No (b) Yes
  27. 27.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 54° and 22°. What is the exterior angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 90° and angle B = 62°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 3 cm, 5 cm and 5 cm? (a) No (b) Yes
  33. 33.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 56° and angle B = 22°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  36. 36.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)?
  37. 37.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  38. 38.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)?
  39. 39.The two interior opposite angles of a triangle are 20° and 26°. What is the exterior angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 39° and 73°. What is the exterior angle (in degrees)?

Answer key

  1. 17
  2. 87
  3. No
  4. 79
  5. 76
  6. 27
  7. 38
  8. 106
  9. 40
  10. Yes
  11. No
  12. 74
  13. 90
  14. 21
  15. 15
  16. 48
  17. 117
  18. 86
  19. 36
  20. 101
  21. 80
  22. 19
  23. 80
  24. 63
  25. No
  26. Yes
  27. 45
  28. 76
  29. 40
  30. 28
  31. 62
  32. Yes
  33. 68
  34. 102
  35. 21
  36. 5
  37. 54
  38. 12
  39. 46
  40. 112

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