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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 615 · 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 two equal angles are 64° each. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 82° and angle B = 34°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  4. 4.An exterior angle of a triangle is 59°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  6. 6.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  7. 7.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  8. 8.In triangle ABC, angle A = 44° and angle B = 57°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (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.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  12. 12.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  13. 13.An exterior angle of a triangle is 158°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  14. 14.Can a triangle have sides of 10 cm, 9 cm and 9 cm? (a) Yes (b) No
  15. 15.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  16. 16.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 56° and angle B = 81°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  19. 19.In triangle ABC, angle A = 51° and angle B = 26°. What is angle C (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  21. 21.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  23. 23.Can a triangle have sides of 5 cm, 12 cm and 8 cm? (a) No (b) Yes
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  26. 26.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 30° and angle B = 62°. What is angle C (in degrees)?
  31. 31.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)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 63° and angle B = 62°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?

Answer key

  1. 52
  2. 64
  3. 36
  4. 24
  5. 25
  6. 17
  7. 55
  8. 79
  9. 50
  10. 76
  11. 5
  12. 55
  13. 79
  14. Yes
  15. 51
  16. 51
  17. 43
  18. 49
  19. 103
  20. 10
  21. 20
  22. 90
  23. Yes
  24. 30
  25. 69
  26. 15
  27. 21
  28. 128
  29. 74
  30. 88
  31. 24
  32. 16
  33. 58
  34. 77
  35. 90
  36. 68
  37. 74
  38. 130
  39. 55
  40. 44

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