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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 389 · 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 90°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 94° and angle B = 44°. What is angle C (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 69° and angle B = 90°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 2 cm, 6 cm and 9 cm? (a) Yes (b) No
  6. 6.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)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  9. 9.Can a triangle have sides of 17 cm, 12 cm and 4 cm? (a) Yes (b) No
  10. 10.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  13. 13.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 79° and 37°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 74° and angle B = 84°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  18. 18.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  20. 20.The two interior opposite angles of a triangle are 70° and 30°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 30° and angle B = 61°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 64° and angle B = 40°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  24. 24.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  25. 25.Can a triangle have sides of 10 cm, 4 cm and 9 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 59° and angle B = 57°. What is angle C (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  28. 28.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  29. 29.Can a triangle have sides of 2 cm, 2 cm and 4 cm? (a) No (b) Yes
  30. 30.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 4 cm, 3 cm and 2 cm? (a) No (b) Yes
  32. 32.The two interior opposite angles of a triangle are 58° and 50°. What is the exterior angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 12 cm, 6 cm and 2 cm? (a) No (b) Yes
  35. 35.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)?
  36. 36.The two interior opposite angles of a triangle are 45° and 65°. What is the exterior angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 59° and angle B = 70°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?

Answer key

  1. 31
  2. 42
  3. 78
  4. 21
  5. No
  6. 8
  7. 29
  8. 36
  9. No
  10. 76
  11. 17
  12. 40
  13. 59
  14. 116
  15. 22
  16. 26
  17. 10
  18. 20
  19. 13
  20. 100
  21. 89
  22. 76
  23. 63
  24. 36
  25. Yes
  26. 64
  27. 39
  28. 46
  29. No
  30. 33
  31. Yes
  32. 108
  33. 70
  34. No
  35. 24
  36. 110
  37. 20
  38. 51
  39. 90
  40. 84

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