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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 72 · 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 66°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 81° and angle B = 69°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  4. 4.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)?
  5. 5.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 18 cm, 12 cm and 5 cm? (a) Yes (b) No
  7. 7.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  10. 10.Can a triangle have sides of 12 cm, 16 cm and 2 cm? (a) Yes (b) No
  11. 11.The two interior opposite angles of a triangle are 70° and 58°. What is the exterior angle (in degrees)?
  12. 12.An exterior angle of a triangle is 133°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 12 cm, 10 cm and 14 cm? (a) No (b) Yes
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  22. 22.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 85° and angle B = 50°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 12 cm, 12 cm and 3 cm? (a) Yes (b) No
  25. 25.In triangle ABC, angle A = 46° and angle B = 34°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 15 cm, 3 cm and 7 cm? (a) No (b) Yes
  27. 27.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  28. 28.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)?
  29. 29.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 14 cm, 5 cm and 5 cm? (a) No (b) Yes
  35. 35.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 39° and 47°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  40. 40.Can a triangle have sides of 11 cm, 2 cm and 6 cm? (a) No (b) Yes

Answer key

  1. 26
  2. 30
  3. 43
  4. 10
  5. 29
  6. No
  7. 98
  8. 90
  9. 7
  10. No
  11. 128
  12. 75
  13. 102
  14. 45
  15. 64
  16. 48
  17. 30
  18. 60
  19. Yes
  20. 36
  21. 25
  22. 65
  23. 45
  24. Yes
  25. 100
  26. No
  27. 100
  28. 8
  29. 30
  30. 26
  31. 36
  32. 40
  33. 136
  34. No
  35. 56
  36. 86
  37. 25
  38. 45
  39. 120
  40. No

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