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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 149 · 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 longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  2. 2.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 25° and 32°. What is the exterior angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  7. 7.Can a triangle have sides of 11 cm, 2 cm and 10 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  13. 13.In triangle ABC, angle A = 29° and angle B = 116°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 23 cm, 12 cm and 10 cm? (a) No (b) Yes
  15. 15.Can a triangle have sides of 3 cm, 14 cm and 6 cm? (a) No (b) Yes
  16. 16.Can a triangle have sides of 8 cm, 16 cm and 7 cm? (a) Yes (b) No
  17. 17.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 43° and angle B = 37°. What is angle C (in degrees)?
  20. 20.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)?
  21. 21.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 5 cm, 5 cm and 3 cm? (a) Yes (b) No
  23. 23.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  26. 26.The two interior opposite angles of a triangle are 54° and 56°. What is the exterior angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 8 cm, 7 cm and 15 cm? (a) Yes (b) No
  29. 29.The two interior opposite angles of a triangle are 20° and 68°. What is the exterior angle (in degrees)?
  30. 30.In triangle ABC, angle A = 96° and angle B = 27°. What is angle C (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  32. 32.In triangle ABC, angle A = 83° and angle B = 46°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 47°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 30° and angle B = 69°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?

Answer key

  1. 18
  2. 76
  3. 65
  4. 57
  5. 90
  6. 90
  7. Yes
  8. 14
  9. 82
  10. 50
  11. 58
  12. 33
  13. 35
  14. No
  15. No
  16. No
  17. 75
  18. 21
  19. 100
  20. 15
  21. 39
  22. Yes
  23. 134
  24. 30
  25. 17
  26. 110
  27. 106
  28. No
  29. 88
  30. 57
  31. 25
  32. 51
  33. 70
  34. 24
  35. 21
  36. 81
  37. 51
  38. 120
  39. 10
  40. 39

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