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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 456 · 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 angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  4. 4.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  7. 7.In triangle ABC, angle A = 63° and angle B = 89°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 6 cm, 6 cm and 6 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 90° and angle B = 21°. What is angle C (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 longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  15. 15.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  16. 16.Can a triangle have sides of 11 cm, 21 cm and 8 cm? (a) Yes (b) No
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  18. 18.In triangle ABC, angle A = 24° and angle B = 22°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 44° and angle B = 41°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 25° and angle B = 29°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 91° and angle B = 64°. What is angle C (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 32° and 66°. What is the exterior angle (in degrees)?
  26. 26.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  27. 27.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  30. 30.Can a triangle have sides of 6 cm, 12 cm and 9 cm? (a) No (b) Yes
  31. 31.In triangle ABC, angle A = 49° and angle B = 109°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 49° and angle B = 98°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 66° and angle B = 27°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  38. 38.Can a triangle have sides of 8 cm, 12 cm and 6 cm? (a) No (b) Yes
  39. 39.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  40. 40.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?

Answer key

  1. 41
  2. 54
  3. 5
  4. 21
  5. 59
  6. 17
  7. 28
  8. 90
  9. 61
  10. 76
  11. Yes
  12. 69
  13. 25
  14. 12
  15. 100
  16. No
  17. 120
  18. 134
  19. 95
  20. 64
  21. 84
  22. 126
  23. 36
  24. 25
  25. 98
  26. 8
  27. 68
  28. 56
  29. 25
  30. Yes
  31. 22
  32. 26
  33. 33
  34. 87
  35. 26
  36. 98
  37. 70
  38. Yes
  39. 6
  40. 108

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