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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 176 · 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 an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 11 cm, 23 cm and 7 cm? (a) No (b) Yes
  3. 3.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 41° and 28°. What is the exterior angle (in degrees)?
  5. 5.Can a triangle have sides of 5 cm, 6 cm and 11 cm? (a) No (b) Yes
  6. 6.In triangle ABC, angle A = 70° and angle B = 52°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  8. 8.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  11. 11.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  13. 13.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 74° and 37°. What is the exterior angle (in degrees)?
  18. 18.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  19. 19.In triangle ABC, angle A = 53° and angle B = 57°. What is angle C (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 51° and 48°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 71° and angle B = 50°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 5 cm and 4 cm? (a) Yes (b) No
  23. 23.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  24. 24.Can a triangle have sides of 12 cm, 3 cm and 10 cm? (a) No (b) Yes
  25. 25.In triangle ABC, angle A = 60° and angle B = 60°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 26° and 46°. What is the exterior angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 6 cm and 15 cm? (a) Yes (b) No
  35. 35.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  37. 37.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  38. 38.Can a triangle have sides of 9 cm, 22 cm and 8 cm? (a) Yes (b) No
  39. 39.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)?
  40. 40.In triangle ABC, angle A = 87° and angle B = 40°. What is angle C (in degrees)?

Answer key

  1. 136
  2. No
  3. 34
  4. 69
  5. No
  6. 58
  7. 71
  8. 58
  9. 49
  10. 19
  11. 40
  12. 10
  13. 75
  14. 67
  15. 90
  16. 90
  17. 111
  18. 12
  19. 70
  20. 99
  21. 59
  22. No
  23. 78
  24. Yes
  25. 60
  26. 75
  27. 49
  28. 44
  29. 70
  30. 72
  31. 54
  32. 39
  33. 72
  34. No
  35. 58
  36. 92
  37. 24
  38. No
  39. 15
  40. 53

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