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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 380 · 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.The two interior opposite angles of a triangle are 23° and 65°. What is the exterior angle (in degrees)?
  2. 2.In triangle ABC, angle A = 73° and angle B = 70°. What is angle C (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  5. 5.Can a triangle have sides of 22 cm, 8 cm and 9 cm? (a) No (b) Yes
  6. 6.Can a triangle have sides of 6 cm, 4 cm and 9 cm? (a) No (b) Yes
  7. 7.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 4 cm, 4 cm and 10 cm? (a) Yes (b) No
  9. 9.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 37° and 63°. What is the exterior angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 66° and 34°. What is the exterior angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 7 cm, 8 cm and 7 cm? (a) No (b) Yes
  19. 19.Can a triangle have sides of 11 cm, 5 cm and 10 cm? (a) No (b) Yes
  20. 20.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  21. 21.Can a triangle have sides of 7 cm, 10 cm and 9 cm? (a) No (b) Yes
  22. 22.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  23. 23.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  24. 24.In triangle ABC, angle A = 92° and angle B = 67°. What is angle C (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  26. 26.In triangle ABC, angle A = 73° and angle B = 73°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 7 cm, 3 cm and 4 cm? (a) No (b) Yes
  28. 28.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  30. 30.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  31. 31.Can a triangle have sides of 10 cm, 23 cm and 10 cm? (a) Yes (b) No
  32. 32.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  33. 33.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 23° and 49°. What is the exterior angle (in degrees)?
  36. 36.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  39. 39.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  40. 40.In triangle ABC, angle A = 43° and angle B = 45°. What is angle C (in degrees)?

Answer key

  1. 88
  2. 37
  3. 39
  4. 29
  5. No
  6. Yes
  7. 53
  8. No
  9. 39
  10. 100
  11. 72
  12. 39
  13. 130
  14. 64
  15. 100
  16. 33
  17. 20
  18. Yes
  19. Yes
  20. 90
  21. Yes
  22. 10
  23. 10
  24. 21
  25. 25
  26. 34
  27. No
  28. 69
  29. 84
  30. 71
  31. No
  32. 65
  33. 33
  34. 43
  35. 72
  36. 20
  37. 30
  38. 72
  39. 3
  40. 92

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