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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 112 · 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.

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  1. 1.In triangle ABC, angle A = 100° and angle B = 29°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 98° and angle B = 57°. What is angle C (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 69° and 43°. What is the exterior angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 39° and angle B = 43°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 55° and angle B = 30°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  10. 10.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 65° and 61°. What is the exterior angle (in degrees)?
  12. 12.Can a triangle have sides of 12 cm, 22 cm and 9 cm? (a) Yes (b) No
  13. 13.Can a triangle have sides of 5 cm, 2 cm and 2 cm? (a) No (b) Yes
  14. 14.Can a triangle have sides of 7 cm, 17 cm and 7 cm? (a) Yes (b) No
  15. 15.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 62° and 55°. What is the exterior angle (in degrees)?
  17. 17.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  18. 18.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 36° and 23°. What is the exterior angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 37° and angle B = 26°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  23. 23.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  24. 24.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  26. 26.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  27. 27.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  30. 30.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  32. 32.In triangle ABC, angle A = 97° and angle B = 20°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 8 cm, 9 cm and 8 cm? (a) No (b) Yes
  34. 34.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  35. 35.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 2 cm, 3 cm and 4 cm? (a) Yes (b) No
  40. 40.An exterior angle of a triangle is 48°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?

Answer key

  1. 51
  2. 90
  3. 25
  4. 112
  5. 72
  6. 98
  7. 95
  8. 30
  9. 41
  10. 21
  11. 126
  12. No
  13. No
  14. No
  15. 40
  16. 117
  17. 24
  18. 24
  19. 59
  20. 59
  21. 117
  22. 35
  23. 56
  24. 20
  25. 77
  26. 6
  27. 34
  28. 43
  29. 41
  30. 28
  31. 45
  32. 63
  33. Yes
  34. 16
  35. 65
  36. 80
  37. 36
  38. 20
  39. Yes
  40. 26

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