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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 978 · 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 an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  2. 2.Can a triangle have sides of 19 cm, 9 cm and 9 cm? (a) No (b) Yes
  3. 3.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  5. 5.Can a triangle have sides of 8 cm, 8 cm and 2 cm? (a) No (b) Yes
  6. 6.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  7. 7.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  8. 8.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  9. 9.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 74° and angle B = 26°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 57° and 56°. What is the exterior angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 3 cm, 13 cm and 10 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 29° and angle B = 121°. What is angle C (in degrees)?
  15. 15.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  16. 16.An exterior angle of a triangle is 45°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 51° and 31°. What is the exterior angle (in degrees)?
  18. 18.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  20. 20.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  21. 21.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 27° and angle B = 76°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 16 cm, 6 cm and 7 cm? (a) No (b) Yes
  27. 27.Can a triangle have sides of 11 cm, 5 cm and 7 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 44° and angle B = 113°. What is angle C (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  30. 30.In triangle ABC, angle A = 24° and angle B = 128°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 23 cm, 11 cm and 8 cm? (a) No (b) Yes
  32. 32.Can a triangle have sides of 11 cm, 8 cm and 16 cm? (a) No (b) Yes
  33. 33.In triangle ABC, angle A = 35° and angle B = 105°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 3 cm, 2 cm and 7 cm? (a) Yes (b) No
  35. 35.Can a triangle have sides of 9 cm, 7 cm and 8 cm? (a) No (b) Yes
  36. 36.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 99° and angle B = 54°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  39. 39.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  40. 40.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?

Answer key

  1. 14
  2. No
  3. 104
  4. 63
  5. Yes
  6. 75
  7. 28
  8. 15
  9. 24
  10. 80
  11. 113
  12. 75
  13. No
  14. 30
  15. 12
  16. 21
  17. 82
  18. 32
  19. 36
  20. 37
  21. 48
  22. 98
  23. 40
  24. 30
  25. 77
  26. No
  27. Yes
  28. 23
  29. 17
  30. 28
  31. No
  32. Yes
  33. 40
  34. No
  35. Yes
  36. 79
  37. 27
  38. 63
  39. 7
  40. 27

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