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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 115 · 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 angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  2. 2.Can a triangle have sides of 12 cm, 22 cm and 9 cm? (a) Yes (b) No
  3. 3.The two interior opposite angles of a triangle are 38° and 68°. What is the exterior angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 61° and 63°. What is the exterior angle (in degrees)?
  5. 5.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 8 cm, 8 cm and 10 cm? (a) No (b) Yes
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  8. 8.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  10. 10.In triangle ABC, angle A = 21° and angle B = 85°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  13. 13.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  14. 14.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  16. 16.Can a triangle have sides of 3 cm, 11 cm and 12 cm? (a) No (b) Yes
  17. 17.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 49° and angle B = 92°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 11 cm, 9 cm and 8 cm? (a) No (b) Yes
  22. 22.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  24. 24.Can a triangle have sides of 9 cm, 7 cm and 12 cm? (a) Yes (b) No
  25. 25.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  26. 26.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  28. 28.In triangle ABC, angle A = 39° and angle B = 37°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  30. 30.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  31. 31.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 8 cm and 8 cm? (a) Yes (b) No
  35. 35.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  36. 36.In triangle ABC, angle A = 66° and angle B = 64°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  39. 39.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 22° and angle B = 39°. What is angle C (in degrees)?

Answer key

  1. 18
  2. No
  3. 106
  4. 124
  5. 21
  6. Yes
  7. 90
  8. 12
  9. 21
  10. 74
  11. 20
  12. 20
  13. 9
  14. 25
  15. 72
  16. Yes
  17. 48
  18. 45
  19. 39
  20. 31
  21. Yes
  22. 33
  23. 17
  24. Yes
  25. 25
  26. 28
  27. 26
  28. 104
  29. 11
  30. 12
  31. 29
  32. 64
  33. 42
  34. Yes
  35. 59
  36. 50
  37. 18
  38. 25
  39. 67
  40. 119

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