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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 53 · 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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 4 cm, 10 cm and 10 cm? (a) No (b) Yes
  2. 2.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 37°. 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 35°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  9. 9.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 50° and angle B = 42°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 21° and angle B = 59°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 18 cm, 8 cm and 7 cm? (a) No (b) Yes
  20. 20.The two interior opposite angles of a triangle are 52° and 35°. What is the exterior angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  24. 24.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)?
  25. 25.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 98° and angle B = 59°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 36° and 34°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 23° and angle B = 82°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 90° and angle B = 39°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 43° and angle B = 51°. What is angle C (in degrees)?

Answer key

  1. Yes
  2. 74
  3. 28
  4. 53
  5. 17
  6. 55
  7. 23
  8. 44
  9. 41
  10. 90
  11. 36
  12. 69
  13. 88
  14. 31
  15. 38
  16. 51
  17. 43
  18. 100
  19. No
  20. 87
  21. 80
  22. 70
  23. 24
  24. 12
  25. 68
  26. 74
  27. 102
  28. 70
  29. 25
  30. 21
  31. 36
  32. 30
  33. 90
  34. 23
  35. 70
  36. 70
  37. 75
  38. 51
  39. 48
  40. 86

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