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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 835 · 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 98°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  2. 2.Can a triangle have sides of 12 cm, 9 cm and 9 cm? (a) Yes (b) No
  3. 3.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  5. 5.In triangle ABC, angle A = 43° and angle B = 47°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 71° and angle B = 44°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  9. 9.In triangle ABC, angle A = 48° and angle B = 47°. What is angle C (in degrees)?
  10. 10.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  11. 11.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  13. 13.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  14. 14.Can a triangle have sides of 5 cm, 8 cm and 7 cm? (a) Yes (b) No
  15. 15.In triangle ABC, angle A = 43° and angle B = 88°. What is angle C (in degrees)?
  16. 16.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)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  18. 18.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 50° and 56°. What is the exterior angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  22. 22.In triangle ABC, angle A = 67° and angle B = 66°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 100° and angle B = 50°. What is angle C (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 66° and 31°. What is the exterior angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  27. 27.Can a triangle have sides of 8 cm, 10 cm and 3 cm? (a) No (b) Yes
  28. 28.In triangle ABC, angle A = 89° and angle B = 65°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 4 cm, 12 cm and 8 cm? (a) No (b) Yes
  32. 32.The two interior opposite angles of a triangle are 31° and 35°. What is the exterior angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  34. 34.Can a triangle have sides of 7 cm, 9 cm and 18 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 47° and 49°. What is the exterior angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  37. 37.An exterior angle of a triangle is 133°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 9 cm, 8 cm and 4 cm? (a) No (b) Yes
  40. 40.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?

Answer key

  1. 54
  2. Yes
  3. 82
  4. 69
  5. 90
  6. 65
  7. 36
  8. 66
  9. 85
  10. 6
  11. 100
  12. 10
  13. 8
  14. Yes
  15. 49
  16. 15
  17. 72
  18. 72
  19. 40
  20. 106
  21. 13
  22. 47
  23. 32
  24. 30
  25. 97
  26. 90
  27. Yes
  28. 26
  29. 120
  30. 22
  31. No
  32. 66
  33. 20
  34. No
  35. 96
  36. 72
  37. 63
  38. 37
  39. Yes
  40. 27

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