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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 962 · 40 sums
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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 44° and 32°. What is the exterior angle (in degrees)?
  2. 2.Can a triangle have sides of 2 cm, 2 cm and 5 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 33° and angle B = 109°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 8 cm, 24 cm and 11 cm? (a) Yes (b) No
  5. 5.Can a triangle have sides of 7 cm, 7 cm and 6 cm? (a) Yes (b) No
  6. 6.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)?
  7. 7.The two interior opposite angles of a triangle are 77° and 62°. What is the exterior angle (in degrees)?
  8. 8.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 13 cm, 9 cm and 12 cm? (a) Yes (b) No
  11. 11.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  13. 13.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  16. 16.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 16 cm, 12 cm and 2 cm? (a) Yes (b) No
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 11 cm, 19 cm and 6 cm? (a) Yes (b) No
  23. 23.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  25. 25.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  26. 26.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 13 cm, 5 cm and 11 cm? (a) No (b) Yes
  28. 28.The two interior opposite angles of a triangle are 46° and 52°. What is the exterior angle (in degrees)?
  29. 29.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  30. 30.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 9 cm, 8 cm and 9 cm? (a) No (b) Yes
  33. 33.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  34. 34.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  35. 35.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 42° and 35°. What is the exterior angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 40° and 46°. What is the exterior angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?

Answer key

  1. 76
  2. No
  3. 38
  4. No
  5. Yes
  6. 36
  7. 139
  8. 45
  9. 61
  10. Yes
  11. 25
  12. 64
  13. 15
  14. 13
  15. 25
  16. 22
  17. 30
  18. No
  19. 30
  20. 39
  21. 10
  22. No
  23. 40
  24. 37
  25. 5
  26. 64
  27. Yes
  28. 98
  29. 45
  30. 75
  31. 16
  32. Yes
  33. 35
  34. 46
  35. 21
  36. 61
  37. 77
  38. 40
  39. 86
  40. 28

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