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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 462 · 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 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  2. 2.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  3. 3.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  7. 7.An exterior angle of a triangle is 148°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 29° and angle B = 82°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  14. 14.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 114°. What is each of the other two angles (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 58° and 21°. What is the exterior angle (in degrees)?
  19. 19.Can a triangle have sides of 22 cm, 9 cm and 12 cm? (a) Yes (b) No
  20. 20.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 5 cm, 8 cm and 6 cm? (a) No (b) Yes
  23. 23.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  25. 25.In triangle ABC, angle A = 77° and angle B = 60°. What is angle C (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  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 triangle ABC, angle A = 87° and angle B = 44°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  30. 30.In triangle ABC, angle A = 44° and angle B = 70°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  32. 32.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)?
  33. 33.In triangle ABC, angle A = 58° and angle B = 98°. What is angle C (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 34° and 68°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 98° and angle B = 50°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 54° and angle B = 70°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?

Answer key

  1. 7
  2. 39
  3. 49
  4. 84
  5. 12
  6. 110
  7. 73
  8. 30
  9. 39
  10. 128
  11. 75
  12. 69
  13. 62
  14. 80
  15. 66
  16. 69
  17. 33
  18. 79
  19. No
  20. 45
  21. 40
  22. Yes
  23. 21
  24. 59
  25. 43
  26. 39
  27. 15
  28. 49
  29. 34
  30. 66
  31. 41
  32. 12
  33. 24
  34. 102
  35. 32
  36. 13
  37. 56
  38. 20
  39. 90
  40. 17

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