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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 447 · 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 10 cm, 12 cm and 25 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  4. 4.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 38° and angle B = 110°. What is angle C (in degrees)?
  7. 7.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)?
  8. 8.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  11. 11.Can a triangle have sides of 4 cm, 5 cm and 5 cm? (a) Yes (b) No
  12. 12.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  15. 15.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 35° and 49°. What is the exterior angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 38° and angle B = 52°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  22. 22.In triangle ABC, angle A = 34° and angle B = 95°. What is angle C (in degrees)?
  23. 23.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)?
  24. 24.In triangle ABC, angle A = 25° and angle B = 89°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 76° and angle B = 38°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 89° and angle B = 58°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 74° and angle B = 57°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 31° and 67°. What is the exterior angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 9 cm, 17 cm and 8 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 21° and angle B = 105°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 4 cm, 6 cm and 9 cm? (a) No (b) Yes
  35. 35.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  36. 36.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 98° and angle B = 20°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  39. 39.Can a triangle have sides of 8 cm, 6 cm and 17 cm? (a) Yes (b) No
  40. 40.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?

Answer key

  1. No
  2. 54
  3. 4
  4. 67
  5. 30
  6. 32
  7. 24
  8. 80
  9. 36
  10. 33
  11. Yes
  12. 72
  13. 72
  14. 124
  15. 28
  16. 72
  17. 84
  18. 120
  19. 90
  20. 20
  21. 66
  22. 51
  23. 36
  24. 66
  25. 54
  26. 66
  27. 33
  28. 49
  29. 98
  30. 40
  31. 63
  32. No
  33. 54
  34. Yes
  35. 39
  36. 98
  37. 62
  38. 90
  39. No
  40. 71

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