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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 946 · 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 two equal angles are 80° each. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  3. 3.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)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 10 cm, 10 cm and 4 cm? (a) Yes (b) No
  8. 8.Can a triangle have sides of 7 cm, 14 cm and 2 cm? (a) Yes (b) No
  9. 9.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  10. 10.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  14. 14.Can a triangle have sides of 22 cm, 9 cm and 9 cm? (a) No (b) Yes
  15. 15.The two interior opposite angles of a triangle are 46° and 49°. What is the exterior angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  18. 18.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 23° and angle B = 43°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 78° and angle B = 56°. What is angle C (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  24. 24.In triangle ABC, angle A = 20° and angle B = 125°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  28. 28.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  29. 29.An exterior angle of a triangle is 47°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  30. 30.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)?
  31. 31.In triangle ABC, angle A = 69° and angle B = 30°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  34. 34.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)?
  35. 35.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 28° and angle B = 45°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 92° and angle B = 38°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 14 cm, 10 cm and 11 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 6 cm, 12 cm and 3 cm? (a) No (b) Yes
  40. 40.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?

Answer key

  1. 20
  2. 20
  3. 15
  4. 30
  5. 45
  6. 33
  7. Yes
  8. No
  9. 13
  10. 62
  11. 71
  12. 36
  13. 20
  14. No
  15. 95
  16. 28
  17. 48
  18. 45
  19. 65
  20. 114
  21. 45
  22. 46
  23. 26
  24. 35
  25. 61
  26. 33
  27. 25
  28. 50
  29. 26
  30. 24
  31. 81
  32. 61
  33. 54
  34. 8
  35. 42
  36. 107
  37. 50
  38. Yes
  39. No
  40. 108

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