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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 823 · 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 18 cm, 7 cm and 7 cm? (a) Yes (b) No
  2. 2.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 69° and 28°. What is the exterior angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 48° and 65°. What is the exterior angle (in degrees)?
  8. 8.In triangle ABC, angle A = 42° and angle B = 24°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 29° and angle B = 50°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  18. 18.In triangle ABC, angle A = 30° and angle B = 30°. What is angle C (in degrees)?
  19. 19.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  20. 20.Can a triangle have sides of 1 cm, 7 cm and 7 cm? (a) No (b) Yes
  21. 21.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  22. 22.In triangle ABC, angle A = 66° and angle B = 58°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 18 cm, 9 cm and 11 cm? (a) No (b) Yes
  24. 24.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)?
  25. 25.The two interior opposite angles of a triangle are 65° and 64°. What is the exterior angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 50° and angle B = 32°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 9 cm, 4 cm and 3 cm? (a) Yes (b) No
  32. 32.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  33. 33.In triangle ABC, angle A = 70° and angle B = 88°. What is angle C (in degrees)?
  34. 34.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)?
  35. 35.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  36. 36.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  39. 39.Can a triangle have sides of 8 cm, 8 cm and 4 cm? (a) No (b) Yes
  40. 40.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?

Answer key

  1. No
  2. 38
  3. 20
  4. 114
  5. 27
  6. 97
  7. 113
  8. 114
  9. 38
  10. 69
  11. 30
  12. 17
  13. 20
  14. 101
  15. 56
  16. 44
  17. 16
  18. 120
  19. 30
  20. Yes
  21. 67
  22. 56
  23. Yes
  24. 24
  25. 129
  26. 23
  27. 30
  28. 30
  29. 48
  30. 98
  31. No
  32. 26
  33. 22
  34. 15
  35. 15
  36. 29
  37. 84
  38. 25
  39. Yes
  40. 90

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