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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 277 · 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.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  3. 3.Can a triangle have sides of 21 cm, 10 cm and 10 cm? (a) Yes (b) No
  4. 4.Can a triangle have sides of 2 cm, 2 cm and 6 cm? (a) No (b) Yes
  5. 5.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  10. 10.In triangle ABC, angle A = 68° and angle B = 21°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  12. 12.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)?
  13. 13.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  14. 14.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  15. 15.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)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 66° and angle B = 84°. What is angle C (in degrees)?
  18. 18.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  24. 24.In triangle ABC, angle A = 51° and angle B = 71°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 11 cm, 10 cm and 22 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 33° and angle B = 55°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 6 cm, 2 cm and 4 cm? (a) No (b) Yes
  30. 30.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  31. 31.Can a triangle have sides of 7 cm, 3 cm and 12 cm? (a) No (b) Yes
  32. 32.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  35. 35.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  36. 36.Can a triangle have sides of 9 cm, 13 cm and 9 cm? (a) Yes (b) No
  37. 37.The two interior opposite angles of a triangle are 56° and 62°. What is the exterior angle (in degrees)?
  38. 38.In triangle ABC, angle A = 27° and angle B = 85°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 79° and angle B = 79°. What is angle C (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?

Answer key

  1. 47
  2. 84
  3. No
  4. No
  5. 69
  6. 90
  7. 134
  8. 41
  9. 25
  10. 91
  11. 18
  12. 12
  13. 39
  14. 8
  15. 36
  16. 36
  17. 30
  18. 34
  19. 114
  20. 16
  21. 65
  22. 120
  23. 64
  24. 58
  25. 68
  26. 14
  27. No
  28. 92
  29. No
  30. 17
  31. No
  32. 60
  33. 46
  34. 18
  35. 72
  36. Yes
  37. 118
  38. 68
  39. 22
  40. 39

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