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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 851 · 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 99°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  2. 2.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)?
  3. 3.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  4. 4.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)?
  5. 5.The two interior opposite angles of a triangle are 51° and 48°. What is the exterior angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  7. 7.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 74° and 65°. What is the exterior angle (in degrees)?
  9. 9.In triangle ABC, angle A = 80° and angle B = 24°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 14 cm and 8 cm? (a) No (b) Yes
  11. 11.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  12. 12.Can a triangle have sides of 4 cm, 15 cm and 7 cm? (a) No (b) Yes
  13. 13.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 10 cm, 6 cm and 6 cm? (a) Yes (b) No
  15. 15.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 73° and angle B = 63°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 12 cm, 21 cm and 7 cm? (a) No (b) Yes
  18. 18.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  19. 19.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  20. 20.In triangle ABC, angle A = 24° and angle B = 102°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 67° and 55°. What is the exterior angle (in degrees)?
  23. 23.Can a triangle have sides of 9 cm, 9 cm and 13 cm? (a) No (b) Yes
  24. 24.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  27. 27.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)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  30. 30.In triangle ABC, angle A = 40° and angle B = 59°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  33. 33.In triangle ABC, angle A = 75° and angle B = 51°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 21 cm, 9 cm and 11 cm? (a) No (b) Yes
  35. 35.In triangle ABC, angle A = 63° and angle B = 70°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 65° and angle B = 48°. What is angle C (in degrees)?
  37. 37.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  39. 39.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?

Answer key

  1. 28
  2. 24
  3. 90
  4. 15
  5. 99
  6. 16
  7. 49
  8. 139
  9. 76
  10. Yes
  11. 45
  12. No
  13. 124
  14. Yes
  15. 68
  16. 44
  17. No
  18. 10
  19. 24
  20. 54
  21. 72
  22. 122
  23. Yes
  24. 108
  25. 27
  26. 32
  27. 15
  28. 62
  29. 51
  30. 81
  31. 30
  32. 15
  33. 54
  34. No
  35. 47
  36. 67
  37. 72
  38. 20
  39. 36
  40. 12

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