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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 698 · 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.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  2. 2.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)?
  3. 3.The two interior opposite angles of a triangle are 36° and 45°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 4 cm, 9 cm and 10 cm? (a) No (b) Yes
  7. 7.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 8 cm, 3 cm and 11 cm? (a) Yes (b) No
  9. 9.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 10 cm, 2 cm and 10 cm? (a) No (b) Yes
  12. 12.The two interior opposite angles of a triangle are 53° and 69°. What is the exterior angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  14. 14.In triangle ABC, angle A = 81° and angle B = 42°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  17. 17.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 64° and angle B = 45°. What is angle C (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  23. 23.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  24. 24.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  26. 26.Can a triangle have sides of 11 cm, 3 cm and 8 cm? (a) No (b) Yes
  27. 27.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  28. 28.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)?
  29. 29.In triangle ABC, angle A = 23° and angle B = 114°. What is angle C (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  31. 31.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  33. 33.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)?
  34. 34.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 69° and angle B = 33°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 98° and angle B = 43°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 9 cm, 19 cm and 6 cm? (a) Yes (b) No
  39. 39.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  40. 40.Can a triangle have sides of 10 cm, 10 cm and 5 cm? (a) No (b) Yes

Answer key

  1. 90
  2. 24
  3. 81
  4. 18
  5. 46
  6. Yes
  7. 27
  8. No
  9. 37
  10. 43
  11. Yes
  12. 122
  13. 39
  14. 57
  15. 18
  16. 77
  17. 40
  18. 34
  19. 30
  20. 30
  21. 71
  22. 13
  23. 26
  24. 25
  25. 39
  26. No
  27. 72
  28. 8
  29. 43
  30. 17
  31. 82
  32. 76
  33. 15
  34. 45
  35. 84
  36. 78
  37. 39
  38. No
  39. 24
  40. Yes

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