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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 482 · 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.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 67° and 45°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 58° and angle B = 26°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 5 cm, 10 cm and 18 cm? (a) Yes (b) No
  6. 6.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  7. 7.In triangle ABC, angle A = 91° and angle B = 44°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  10. 10.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  12. 12.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  13. 13.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)?
  14. 14.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  19. 19.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)?
  20. 20.An exterior angle of a triangle is 42°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 7 cm, 22 cm and 12 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 94° and angle B = 30°. What is angle C (in degrees)?
  24. 24.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)?
  25. 25.In triangle ABC, angle A = 70° and angle B = 88°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 5 cm, 7 cm and 8 cm? (a) No (b) Yes
  27. 27.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  28. 28.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)?
  29. 29.Can a triangle have sides of 10 cm, 7 cm and 22 cm? (a) Yes (b) No
  30. 30.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 5 cm, 6 cm and 12 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 66° and angle B = 35°. What is angle C (in degrees)?
  34. 34.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 5 cm, 8 cm and 7 cm? (a) No (b) Yes
  37. 37.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  38. 38.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)?
  39. 39.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 52° and angle B = 28°. What is angle C (in degrees)?

Answer key

  1. 22
  2. 80
  3. 112
  4. 96
  5. No
  6. 50
  7. 45
  8. 37
  9. 13
  10. 25
  11. 18
  12. 35
  13. 18
  14. 45
  15. 70
  16. 100
  17. 75
  18. 23
  19. 24
  20. 21
  21. 18
  22. No
  23. 56
  24. 7
  25. 22
  26. Yes
  27. 48
  28. 12
  29. No
  30. 25
  31. 58
  32. No
  33. 79
  34. 75
  35. 72
  36. Yes
  37. 20
  38. 12
  39. 70
  40. 100

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