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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 491 · 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 52°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  6. 6.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 98° and angle B = 36°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 3 cm, 5 cm and 2 cm? (a) No (b) Yes
  10. 10.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 59° and angle B = 99°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 56° and 23°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 8 cm, 8 cm and 6 cm? (a) Yes (b) No
  17. 17.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  19. 19.In triangle ABC, angle A = 99° and angle B = 23°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  22. 22.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 29° and 21°. What is the exterior angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  29. 29.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)?
  30. 30.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  31. 31.Can a triangle have sides of 12 cm, 25 cm and 8 cm? (a) Yes (b) No
  32. 32.Can a triangle have sides of 12 cm, 6 cm and 8 cm? (a) Yes (b) No
  33. 33.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 6 cm, 2 cm and 7 cm? (a) Yes (b) No
  38. 38.Can a triangle have sides of 3 cm, 9 cm and 7 cm? (a) Yes (b) No
  39. 39.In triangle ABC, angle A = 25° and angle B = 39°. What is angle C (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?

Answer key

  1. 38
  2. 26
  3. 11
  4. 84
  5. 39
  6. 30
  7. 46
  8. 44
  9. No
  10. 54
  11. 22
  12. 29
  13. 25
  14. 120
  15. 79
  16. Yes
  17. 20
  18. 5
  19. 58
  20. 14
  21. 17
  22. 116
  23. 50
  24. 45
  25. 13
  26. 90
  27. 20
  28. 45
  29. 8
  30. 20
  31. No
  32. Yes
  33. 70
  34. 100
  35. 73
  36. 120
  37. Yes
  38. Yes
  39. 116
  40. 36

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