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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 267 · 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 angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  2. 2.Can a triangle have sides of 2 cm, 7 cm and 12 cm? (a) Yes (b) No
  3. 3.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  5. 5.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 21 cm, 7 cm and 11 cm? (a) No (b) Yes
  7. 7.The two interior opposite angles of a triangle are 27° and 39°. What is the exterior angle (in degrees)?
  8. 8.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 68° and angle B = 29°. What is angle C (in degrees)?
  11. 11.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 20° and 48°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 45° and angle B = 41°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 12 cm, 4 cm and 6 cm? (a) No (b) Yes
  19. 19.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 98° and angle B = 42°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 69° and angle B = 50°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 20 cm, 10 cm and 6 cm? (a) Yes (b) No
  24. 24.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  25. 25.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)?
  26. 26.Can a triangle have sides of 7 cm, 7 cm and 17 cm? (a) Yes (b) No
  27. 27.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 74° and angle B = 72°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 7 cm, 8 cm and 8 cm? (a) No (b) Yes
  32. 32.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  35. 35.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 31° and 27°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  38. 38.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  39. 39.In triangle ABC, angle A = 22° and angle B = 59°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 82° and angle B = 55°. What is angle C (in degrees)?

Answer key

  1. 45
  2. No
  3. 15
  4. 40
  5. 34
  6. No
  7. 66
  8. 49
  9. 71
  10. 83
  11. 12
  12. 67
  13. 49
  14. 68
  15. 94
  16. 54
  17. 37
  18. No
  19. 40
  20. 46
  21. 40
  22. 61
  23. No
  24. 72
  25. 24
  26. No
  27. 51
  28. 14
  29. 34
  30. 53
  31. Yes
  32. 100
  33. 48
  34. 18
  35. 50
  36. 58
  37. 28
  38. 54
  39. 99
  40. 43

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