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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 557 · 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 = 54° and angle B = 26°. What is angle C (in degrees)?
  2. 2.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  3. 3.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 20 cm, 8 cm and 12 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 8 cm, 8 cm and 21 cm? (a) Yes (b) No
  9. 9.Can a triangle have sides of 12 cm, 12 cm and 2 cm? (a) No (b) Yes
  10. 10.In triangle ABC, angle A = 55° and angle B = 34°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 11 cm, 10 cm and 24 cm? (a) No (b) Yes
  12. 12.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 11 cm, 4 cm and 6 cm? (a) Yes (b) No
  14. 14.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 24° and 22°. What is the exterior angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 69° and 76°. What is the exterior angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  20. 20.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  21. 21.In triangle ABC, angle A = 66° and angle B = 87°. What is angle C (in degrees)?
  22. 22.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)?
  23. 23.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  24. 24.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 37° and angle B = 108°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 74° and angle B = 65°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 7 cm, 3 cm and 14 cm? (a) No (b) Yes
  30. 30.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 32° and 75°. What is the exterior angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 70° and 57°. What is the exterior angle (in degrees)?

Answer key

  1. 100
  2. 3
  3. 72
  4. 90
  5. No
  6. 58
  7. 75
  8. No
  9. Yes
  10. 91
  11. No
  12. 14
  13. No
  14. 30
  15. 122
  16. 46
  17. 145
  18. 45
  19. 128
  20. 24
  21. 27
  22. 7
  23. 39
  24. 18
  25. 35
  26. 80
  27. 126
  28. 41
  29. No
  30. 24
  31. 20
  32. 25
  33. 36
  34. 22
  35. 107
  36. 33
  37. 57
  38. 54
  39. 31
  40. 127

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