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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 197 · 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.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 9 cm, 7 cm and 16 cm? (a) No (b) Yes
  5. 5.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  6. 6.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  9. 9.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  11. 11.Can a triangle have sides of 7 cm, 7 cm and 11 cm? (a) No (b) Yes
  12. 12.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 41° and 58°. What is the exterior angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 75° and 20°. What is the exterior angle (in degrees)?
  19. 19.Can a triangle have sides of 7 cm, 11 cm and 7 cm? (a) Yes (b) No
  20. 20.The two interior opposite angles of a triangle are 45° and 43°. What is the exterior angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 61° and 53°. What is the exterior angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 25° and 23°. What is the exterior angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  25. 25.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  27. 27.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)?
  28. 28.An exterior angle of a triangle is 143°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  29. 29.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 39° and angle B = 91°. What is angle C (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  33. 33.In triangle ABC, angle A = 46° and angle B = 93°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  35. 35.Can a triangle have sides of 2 cm, 13 cm and 7 cm? (a) No (b) Yes
  36. 36.The two interior opposite angles of a triangle are 72° and 33°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 32° and angle B = 102°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 11 cm, 16 cm and 5 cm? (a) No (b) Yes
  40. 40.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?

Answer key

  1. 96
  2. 36
  3. 24
  4. No
  5. 17
  6. 18
  7. 79
  8. 25
  9. 62
  10. 25
  11. Yes
  12. 26
  13. 99
  14. 32
  15. 53
  16. 77
  17. 71
  18. 95
  19. Yes
  20. 88
  21. 114
  22. 48
  23. 66
  24. 21
  25. 75
  26. 54
  27. 5
  28. 66
  29. 30
  30. 98
  31. 50
  32. 17
  33. 41
  34. 56
  35. No
  36. 105
  37. 61
  38. 46
  39. No
  40. 31

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