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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 919 · 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.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)?
  2. 2.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  5. 5.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  6. 6.Can a triangle have sides of 25 cm, 10 cm and 10 cm? (a) Yes (b) No
  7. 7.The two interior opposite angles of a triangle are 74° and 64°. What is the exterior angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 50° and 53°. What is the exterior angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  10. 10.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  11. 11.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  14. 14.In triangle ABC, angle A = 77° and angle B = 33°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 31° and angle B = 51°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 33° and angle B = 101°. What is angle C (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  18. 18.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)?
  19. 19.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 71° and angle B = 43°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 75° and angle B = 60°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 64° and angle B = 95°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 34° and angle B = 35°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 44° and angle B = 64°. What is angle C (in degrees)?
  26. 26.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  27. 27.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 42° and angle B = 76°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 92° and angle B = 22°. What is angle C (in degrees)?
  33. 33.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  34. 34.The two interior opposite angles of a triangle are 54° and 25°. What is the exterior angle (in degrees)?
  35. 35.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  36. 36.In triangle ABC, angle A = 53° and angle B = 72°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 94° and angle B = 32°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?

Answer key

  1. 18
  2. 75
  3. 9
  4. 17
  5. 90
  6. No
  7. 138
  8. 103
  9. 39
  10. 24
  11. 42
  12. 35
  13. 25
  14. 70
  15. 98
  16. 46
  17. 23
  18. 24
  19. 67
  20. 60
  21. 66
  22. 45
  23. 21
  24. 111
  25. 72
  26. 79
  27. 84
  28. 64
  29. 62
  30. 134
  31. 40
  32. 66
  33. 15
  34. 79
  35. 26
  36. 55
  37. 14
  38. 54
  39. 55
  40. 54

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