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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 858 · 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 48°. What is the other one (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  4. 4.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)?
  5. 5.The two interior opposite angles of a triangle are 78° and 79°. What is the exterior angle (in degrees)?
  6. 6.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  7. 7.In triangle ABC, angle A = 45° and angle B = 111°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  9. 9.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)?
  10. 10.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 69° and angle B = 42°. What is angle C (in degrees)?
  13. 13.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  17. 17.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  18. 18.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)?
  19. 19.The two interior opposite angles of a triangle are 30° and 70°. What is the exterior angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  25. 25.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)?
  26. 26.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  27. 27.In triangle ABC, angle A = 64° and angle B = 42°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 50° and angle B = 85°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 6 cm, 12 cm and 19 cm? (a) Yes (b) No
  30. 30.Can a triangle have sides of 11 cm, 15 cm and 9 cm? (a) No (b) Yes
  31. 31.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  32. 32.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  33. 33.In triangle ABC, angle A = 70° and angle B = 86°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 69° and angle B = 32°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 145°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 76° and angle B = 45°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 20° and angle B = 40°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 10 cm, 5 cm and 12 cm? (a) No (b) Yes
  40. 40.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?

Answer key

  1. 24
  2. 75
  3. 100
  4. 24
  5. 157
  6. 34
  7. 24
  8. 32
  9. 7
  10. 55
  11. 11
  12. 69
  13. 70
  14. 90
  15. 102
  16. 20
  17. 62
  18. 10
  19. 100
  20. 40
  21. 26
  22. 59
  23. 70
  24. 84
  25. 15
  26. 79
  27. 74
  28. 45
  29. No
  30. Yes
  31. 29
  32. 36
  33. 24
  34. 79
  35. 68
  36. 59
  37. 120
  38. 43
  39. Yes
  40. 39

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