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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 991 · 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.Can a triangle have sides of 5 cm, 12 cm and 17 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 49° and angle B = 34°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  9. 9.Can a triangle have sides of 4 cm, 7 cm and 7 cm? (a) No (b) Yes
  10. 10.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 6 cm, 5 cm and 4 cm? (a) Yes (b) No
  12. 12.Can a triangle have sides of 6 cm, 17 cm and 11 cm? (a) Yes (b) No
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.Can a triangle have sides of 12 cm, 6 cm and 6 cm? (a) No (b) Yes
  15. 15.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 30° and angle B = 111°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 69° and 36°. What is the exterior angle (in degrees)?
  22. 22.In triangle ABC, angle A = 59° and angle B = 20°. What is angle C (in degrees)?
  23. 23.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)?
  24. 24.The two interior opposite angles of a triangle are 65° and 20°. What is the exterior angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 35° and 51°. What is the exterior angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  31. 31.Can a triangle have sides of 21 cm, 11 cm and 9 cm? (a) No (b) Yes
  32. 32.Can a triangle have sides of 11 cm, 23 cm and 10 cm? (a) No (b) Yes
  33. 33.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  35. 35.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  36. 36.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  37. 37.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  38. 38.In triangle ABC, angle A = 67° and angle B = 79°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 44°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?

Answer key

  1. No
  2. 56
  3. 116
  4. 118
  5. 97
  6. 59
  7. 33
  8. 25
  9. Yes
  10. 69
  11. Yes
  12. No
  13. 80
  14. No
  15. 37
  16. 65
  17. 65
  18. 72
  19. 39
  20. 57
  21. 105
  22. 101
  23. 36
  24. 85
  25. 22
  26. 63
  27. 36
  28. 86
  29. 28
  30. 72
  31. No
  32. No
  33. 71
  34. 46
  35. 7
  36. 88
  37. 56
  38. 34
  39. 21
  40. 46

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