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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 352 · 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 20 cm, 12 cm and 4 cm? (a) Yes (b) No
  2. 2.Can a triangle have sides of 8 cm, 11 cm and 4 cm? (a) No (b) Yes
  3. 3.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  4. 4.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)?
  5. 5.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 26° and 23°. What is the exterior angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 40° and 44°. What is the exterior angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 31° and 34°. What is the exterior angle (in degrees)?
  9. 9.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 9 cm, 15 cm and 2 cm? (a) Yes (b) No
  11. 11.The two interior opposite angles of a triangle are 30° and 58°. What is the exterior angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  15. 15.In triangle ABC, angle A = 23° and angle B = 88°. What is angle C (in degrees)?
  16. 16.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)?
  17. 17.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  18. 18.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 36° and 62°. What is the exterior angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 65° and 31°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 62° and angle B = 60°. What is angle C (in degrees)?
  28. 28.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 62° and angle B = 26°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 6 cm, 7 cm and 3 cm? (a) Yes (b) No
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 30° and angle B = 126°. What is angle C (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  36. 36.In triangle ABC, angle A = 38° and angle B = 113°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?

Answer key

  1. No
  2. Yes
  3. 71
  4. 7
  5. 80
  6. 49
  7. 84
  8. 65
  9. 43
  10. No
  11. 88
  12. 46
  13. 11
  14. 39
  15. 69
  16. 24
  17. 28
  18. 23
  19. 84
  20. 98
  21. 36
  22. 57
  23. 96
  24. 66
  25. 20
  26. 21
  27. 58
  28. 15
  29. 20
  30. 67
  31. 92
  32. Yes
  33. 90
  34. 24
  35. 17
  36. 29
  37. 29
  38. 62
  39. 45
  40. 47

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