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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 196 · 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.In triangle ABC, angle A = 31° and angle B = 91°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 22 cm, 11 cm and 7 cm? (a) No (b) Yes
  3. 3.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 24° and angle B = 50°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  8. 8.Can a triangle have sides of 16 cm, 11 cm and 7 cm? (a) No (b) Yes
  9. 9.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)?
  10. 10.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 2 cm, 5 cm and 8 cm? (a) Yes (b) No
  12. 12.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 87° and angle B = 32°. What is angle C (in degrees)?
  16. 16.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)?
  17. 17.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  18. 18.Can a triangle have sides of 10 cm, 11 cm and 7 cm? (a) No (b) Yes
  19. 19.Can a triangle have sides of 8 cm, 21 cm and 11 cm? (a) Yes (b) No
  20. 20.In triangle ABC, angle A = 90° and angle B = 58°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 36° and 26°. What is the exterior angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  27. 27.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 6 cm, 9 cm and 3 cm? (a) Yes (b) No
  29. 29.Can a triangle have sides of 9 cm, 9 cm and 22 cm? (a) No (b) Yes
  30. 30.In triangle ABC, angle A = 28° and angle B = 128°. What is angle C (in degrees)?
  31. 31.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)?
  32. 32.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  33. 33.In triangle ABC, angle A = 46° and angle B = 30°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 2 cm, 3 cm and 8 cm? (a) No (b) Yes
  35. 35.In triangle ABC, angle A = 26° and angle B = 53°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 35° and 20°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  38. 38.In triangle ABC, angle A = 29° and angle B = 115°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  40. 40.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?

Answer key

  1. 58
  2. No
  3. 20
  4. 14
  5. 18
  6. 106
  7. 54
  8. Yes
  9. 12
  10. 27
  11. No
  12. 27
  13. 28
  14. 90
  15. 61
  16. 36
  17. 8
  18. Yes
  19. No
  20. 32
  21. 16
  22. 74
  23. 40
  24. 106
  25. 62
  26. 15
  27. 82
  28. No
  29. No
  30. 24
  31. 15
  32. 41
  33. 104
  34. No
  35. 101
  36. 55
  37. 37
  38. 36
  39. 30
  40. 70

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