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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 626 · 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.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 12 cm, 6 cm and 11 cm? (a) No (b) Yes
  4. 4.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  5. 5.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 41° and angle B = 37°. What is angle C (in degrees)?
  8. 8.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  12. 12.In triangle ABC, angle A = 53° and angle B = 59°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  14. 14.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  15. 15.Can a triangle have sides of 13 cm, 2 cm and 12 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 66° and angle B = 42°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  20. 20.The two interior opposite angles of a triangle are 54° and 28°. What is the exterior angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 19 cm, 8 cm and 10 cm? (a) Yes (b) No
  23. 23.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)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  25. 25.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  26. 26.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  27. 27.In triangle ABC, angle A = 71° and angle B = 77°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 9 cm, 7 cm and 19 cm? (a) Yes (b) No
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  30. 30.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  31. 31.The two interior opposite angles of a triangle are 29° and 57°. What is the exterior angle (in degrees)?
  32. 32.In triangle ABC, angle A = 60° and angle B = 56°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  34. 34.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  35. 35.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)?
  36. 36.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 5 cm, 6 cm and 10 cm? (a) Yes (b) No
  40. 40.Can a triangle have sides of 8 cm, 10 cm and 23 cm? (a) No (b) Yes

Answer key

  1. 49
  2. 62
  3. Yes
  4. 60
  5. 58
  6. 30
  7. 102
  8. 67
  9. 24
  10. 110
  11. 23
  12. 68
  13. 48
  14. 39
  15. Yes
  16. 72
  17. 29
  18. 76
  19. 20
  20. 82
  21. 94
  22. No
  23. 24
  24. 80
  25. 68
  26. 12
  27. 32
  28. No
  29. 120
  30. 15
  31. 86
  32. 64
  33. 90
  34. 76
  35. 15
  36. 24
  37. 25
  38. 49
  39. Yes
  40. No

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