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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 779 · 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 a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 10 cm and 7 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 51° and angle B = 103°. What is angle C (in degrees)?
  4. 4.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  9. 9.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)?
  10. 10.Can a triangle have sides of 10 cm, 15 cm and 9 cm? (a) Yes (b) No
  11. 11.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  13. 13.An exterior angle of a triangle is 158°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 73° and 64°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 6 cm, 2 cm and 7 cm? (a) No (b) Yes
  17. 17.In triangle ABC, angle A = 25° and angle B = 117°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 65° and angle B = 59°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 56° and angle B = 27°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  21. 21.Can a triangle have sides of 10 cm, 6 cm and 2 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 38° and angle B = 82°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 4 cm, 15 cm and 9 cm? (a) Yes (b) No
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  27. 27.An exterior angle of a triangle is 155°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  28. 28.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  29. 29.In triangle ABC, angle A = 44° and angle B = 71°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 90° and angle B = 66°. What is angle C (in degrees)?
  31. 31.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)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 55° and angle B = 25°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  36. 36.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  37. 37.Can a triangle have sides of 7 cm, 8 cm and 15 cm? (a) Yes (b) No
  38. 38.Can a triangle have sides of 8 cm, 13 cm and 2 cm? (a) Yes (b) No
  39. 39.In triangle ABC, angle A = 66° and angle B = 73°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 12 cm, 8 cm and 7 cm? (a) Yes (b) No

Answer key

  1. 67
  2. Yes
  3. 26
  4. 15
  5. 18
  6. 58
  7. 10
  8. 71
  9. 10
  10. Yes
  11. 72
  12. 35
  13. 78
  14. 137
  15. 112
  16. Yes
  17. 38
  18. 56
  19. 97
  20. 68
  21. No
  22. 36
  23. 44
  24. 60
  25. No
  26. 75
  27. 76
  28. 20
  29. 65
  30. 24
  31. 24
  32. 36
  33. 100
  34. 37
  35. 25
  36. 38
  37. No
  38. No
  39. 41
  40. Yes

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