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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 56 · 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 100°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  2. 2.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 40° and angle B = 106°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 70° and 54°. What is the exterior angle (in degrees)?
  11. 11.In triangle ABC, angle A = 28° and angle B = 72°. What is angle C (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 66° and angle B = 47°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 89° and angle B = 56°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  17. 17.Can a triangle have sides of 3 cm, 6 cm and 12 cm? (a) Yes (b) No
  18. 18.Can a triangle have sides of 10 cm, 23 cm and 10 cm? (a) Yes (b) No
  19. 19.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)?
  20. 20.In triangle ABC, angle A = 55° and angle B = 41°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 99° and angle B = 55°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 96° and angle B = 60°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  38. 38.Can a triangle have sides of 22 cm, 9 cm and 11 cm? (a) Yes (b) No
  39. 39.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  40. 40.In triangle ABC, angle A = 96° and angle B = 50°. What is angle C (in degrees)?

Answer key

  1. 79
  2. 66
  3. 73
  4. 78
  5. 112
  6. 34
  7. 76
  8. 30
  9. 68
  10. 124
  11. 80
  12. 90
  13. 78
  14. 67
  15. 35
  16. 30
  17. No
  18. No
  19. 8
  20. 84
  21. 72
  22. 26
  23. 30
  24. 138
  25. 46
  26. 62
  27. 17
  28. 32
  29. 18
  30. 57
  31. 40
  32. 70
  33. 37
  34. 118
  35. 15
  36. 24
  37. 48
  38. No
  39. 17
  40. 34

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