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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 898 · 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 triangle ABC, angle A = 87° and angle B = 23°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 85° and angle B = 60°. What is angle C (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 70° and 26°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 32° and angle B = 42°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 99° and angle B = 47°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 10 cm, 12 cm and 10 cm? (a) No (b) Yes
  7. 7.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  8. 8.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)?
  9. 9.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 46° and 45°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 24° and angle B = 45°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  17. 17.Can a triangle have sides of 7 cm, 12 cm and 21 cm? (a) Yes (b) No
  18. 18.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 31° and angle B = 70°. What is angle C (in degrees)?
  22. 22.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 38° and angle B = 109°. What is angle C (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 59° and 65°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  31. 31.Can a triangle have sides of 8 cm, 7 cm and 6 cm? (a) Yes (b) No
  32. 32.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 60° and 22°. What is the exterior angle (in degrees)?
  34. 34.Can a triangle have sides of 11 cm, 7 cm and 3 cm? (a) No (b) Yes
  35. 35.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  36. 36.The two interior opposite angles of a triangle are 38° and 29°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 71° and angle B = 27°. What is angle C (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 76°. What is each of the other two angles (in degrees)?
  40. 40.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?

Answer key

  1. 70
  2. 35
  3. 96
  4. 106
  5. 34
  6. Yes
  7. 7
  8. 5
  9. 130
  10. 18
  11. 91
  12. 111
  13. 37
  14. 84
  15. 20
  16. 17
  17. No
  18. 12
  19. 36
  20. 52
  21. 79
  22. 10
  23. 20
  24. 17
  25. 36
  26. 33
  27. 124
  28. 22
  29. 56
  30. 120
  31. Yes
  32. 12
  33. 82
  34. No
  35. 5
  36. 67
  37. 82
  38. 39
  39. 52
  40. 12

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