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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 383 · 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 longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  2. 2.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 8 cm, 10 cm and 20 cm? (a) Yes (b) No
  5. 5.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 9 cm, 20 cm and 11 cm? (a) No (b) Yes
  7. 7.The two interior opposite angles of a triangle are 46° and 36°. What is the exterior angle (in degrees)?
  8. 8.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 34° and 27°. What is the exterior angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  12. 12.Can a triangle have sides of 3 cm, 14 cm and 10 cm? (a) Yes (b) No
  13. 13.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  17. 17.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  18. 18.In triangle ABC, angle A = 37° and angle B = 25°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 74° and 61°. What is the exterior angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  22. 22.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 23 cm, 8 cm and 10 cm? (a) No (b) Yes
  25. 25.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 82° and angle B = 39°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 20 cm, 12 cm and 9 cm? (a) Yes (b) No
  28. 28.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  29. 29.The two interior opposite angles of a triangle are 34° and 63°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  32. 32.In triangle ABC, angle A = 91° and angle B = 23°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 72° and 57°. What is the exterior angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 94° and angle B = 40°. What is angle C (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 70° and angle B = 49°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 29° and angle B = 73°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?

Answer key

  1. 24
  2. 33
  3. 80
  4. No
  5. 74
  6. No
  7. 82
  8. 37
  9. 66
  10. 61
  11. 60
  12. No
  13. 62
  14. 61
  15. 75
  16. 15
  17. 45
  18. 118
  19. 90
  20. 135
  21. 17
  22. 112
  23. 80
  24. No
  25. 57
  26. 59
  27. Yes
  28. 39
  29. 97
  30. 40
  31. 58
  32. 66
  33. 138
  34. 129
  35. 34
  36. 46
  37. 120
  38. 61
  39. 78
  40. 38

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