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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 173 · 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 36°. What is the third angle (in degrees)?
  2. 2.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  9. 9.Can a triangle have sides of 9 cm, 2 cm and 6 cm? (a) Yes (b) No
  10. 10.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  13. 13.Can a triangle have sides of 7 cm, 5 cm and 4 cm? (a) Yes (b) No
  14. 14.Can a triangle have sides of 3 cm, 2 cm and 2 cm? (a) No (b) Yes
  15. 15.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 71° and angle B = 24°. What is angle C (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  19. 19.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  22. 22.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  24. 24.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  25. 25.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  27. 27.Can a triangle have sides of 5 cm, 16 cm and 10 cm? (a) Yes (b) No
  28. 28.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  30. 30.Can a triangle have sides of 11 cm, 7 cm and 23 cm? (a) No (b) Yes
  31. 31.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 47° and angle B = 67°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 6 cm, 4 cm and 8 cm? (a) No (b) Yes
  37. 37.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 34° and angle B = 44°. What is angle C (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?

Answer key

  1. 54
  2. 41
  3. 45
  4. 20
  5. 90
  6. 27
  7. 54
  8. 20
  9. No
  10. 5
  11. 31
  12. 20
  13. Yes
  14. Yes
  15. 52
  16. 84
  17. 85
  18. 26
  19. 23
  20. 47
  21. 25
  22. 30
  23. 90
  24. 30
  25. 55
  26. 80
  27. No
  28. 13
  29. 72
  30. No
  31. 60
  32. 17
  33. 64
  34. 49
  35. 66
  36. Yes
  37. 57
  38. 38
  39. 102
  40. 20

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