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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 728 · 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 = 21° and angle B = 127°. What is angle C (in degrees)?
  2. 2.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  3. 3.An exterior angle of a triangle is 135°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 68° and 27°. What is the exterior angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 75° and 22°. What is the exterior angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  10. 10.In triangle ABC, angle A = 90° and angle B = 59°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  12. 12.In triangle ABC, angle A = 67° and angle B = 58°. What is angle C (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 51° and angle B = 47°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 87° and angle B = 27°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 33° and 30°. What is the exterior angle (in degrees)?
  21. 21.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 76° and 67°. What is the exterior angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  24. 24.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)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 62° and angle B = 64°. What is angle C (in degrees)?
  27. 27.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)?
  28. 28.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 41° and angle B = 53°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 29° and 42°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 52° and angle B = 94°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 68° and angle B = 30°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  36. 36.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  37. 37.In triangle ABC, angle A = 72° and angle B = 31°. What is angle C (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  39. 39.In triangle ABC, angle A = 23° and angle B = 91°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?

Answer key

  1. 32
  2. 20
  3. 68
  4. 95
  5. 79
  6. 72
  7. 84
  8. 97
  9. 20
  10. 31
  11. 54
  12. 55
  13. 45
  14. 82
  15. 66
  16. 40
  17. 57
  18. 37
  19. 48
  20. 63
  21. 8
  22. 143
  23. 136
  24. 12
  25. 80
  26. 54
  27. 15
  28. 104
  29. 18
  30. 86
  31. 110
  32. 71
  33. 34
  34. 82
  35. 77
  36. 8
  37. 77
  38. 25
  39. 66
  40. 32

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