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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 578 · 40 sums
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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 interior opposite angles of a triangle are 26° and 36°. What is the exterior angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 28° and 46°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 50° and 62°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 85° and angle B = 68°. What is angle C (in degrees)?
  11. 11.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  13. 13.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)?
  14. 14.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  17. 17.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)?
  18. 18.In triangle ABC, angle A = 36° and angle B = 24°. What is angle C (in degrees)?
  19. 19.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  20. 20.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  21. 21.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)?
  22. 22.In triangle ABC, angle A = 36° and angle B = 21°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 61° and angle B = 98°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 96° and angle B = 28°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 94° and angle B = 38°. What is angle C (in degrees)?
  29. 29.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  30. 30.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  31. 31.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 31° and angle B = 40°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 5 cm, 16 cm and 11 cm? (a) Yes (b) No
  35. 35.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  37. 37.In triangle ABC, angle A = 83° and angle B = 27°. What is angle C (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  39. 39.The two interior opposite angles of a triangle are 31° and 61°. What is the exterior angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?

Answer key

  1. 62
  2. 52
  3. 74
  4. 48
  5. 17
  6. 38
  7. 44
  8. 63
  9. 112
  10. 27
  11. 24
  12. 45
  13. 24
  14. 110
  15. 45
  16. 40
  17. 15
  18. 120
  19. 6
  20. 24
  21. 24
  22. 123
  23. 21
  24. 33
  25. 120
  26. 18
  27. 56
  28. 48
  29. 4
  30. 20
  31. 32
  32. 72
  33. 109
  34. No
  35. 13
  36. 59
  37. 70
  38. 25
  39. 92
  40. 16

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