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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 368 · 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 two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  2. 2.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  10. 10.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 99° and angle B = 40°. What is angle C (in degrees)?
  12. 12.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 66°. What is the other one (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.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 44° and angle B = 80°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 100° and angle B = 34°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  23. 23.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)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 57° and 48°. What is the exterior angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 41° and 27°. What is the exterior angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 65° and 47°. What is the exterior angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 20° and angle B = 92°. What is angle C (in degrees)?
  36. 36.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)?
  37. 37.The two interior opposite angles of a triangle are 30° and 49°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 31° and 74°. What is the exterior angle (in degrees)?

Answer key

  1. 13
  2. 45
  3. 23
  4. 80
  5. 18
  6. 38
  7. 26
  8. 68
  9. 15
  10. 26
  11. 41
  12. 23
  13. 25
  14. 72
  15. 20
  16. 120
  17. 67
  18. 56
  19. 46
  20. 54
  21. 30
  22. 13
  23. 7
  24. 67
  25. 36
  26. 105
  27. 30
  28. 22
  29. 102
  30. 35
  31. 68
  32. 73
  33. 112
  34. 60
  35. 68
  36. 9
  37. 79
  38. 51
  39. 90
  40. 105

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