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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 710 · 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.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  2. 2.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  3. 3.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 56° and angle B = 88°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  9. 9.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)?
  10. 10.In triangle ABC, angle A = 66° and angle B = 70°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  15. 15.In triangle ABC, angle A = 43° and angle B = 100°. What is angle C (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 93° and angle B = 27°. What is angle C (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 22° and 61°. What is the exterior angle (in degrees)?
  26. 26.In triangle ABC, angle A = 79° and angle B = 27°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 3 cm, 5 cm and 12 cm? (a) Yes (b) No
  28. 28.Can a triangle have sides of 12 cm, 12 cm and 4 cm? (a) Yes (b) No
  29. 29.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  32. 32.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)?
  33. 33.The two interior opposite angles of a triangle are 20° and 72°. What is the exterior angle (in degrees)?
  34. 34.Can a triangle have sides of 9 cm, 2 cm and 8 cm? (a) Yes (b) No
  35. 35.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 62°. What is the other one (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 = 58° and angle B = 72°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 8 cm, 9 cm and 4 cm? (a) No (b) Yes
  39. 39.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  40. 40.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?

Answer key

  1. 40
  2. 49
  3. 18
  4. 48
  5. 36
  6. 29
  7. 136
  8. 17
  9. 6
  10. 44
  11. 20
  12. 31
  13. 90
  14. 90
  15. 37
  16. 92
  17. 50
  18. 52
  19. 100
  20. 20
  21. 15
  22. 60
  23. 17
  24. 27
  25. 83
  26. 74
  27. No
  28. Yes
  29. 12
  30. 102
  31. 18
  32. 24
  33. 92
  34. Yes
  35. 35
  36. 13
  37. 50
  38. Yes
  39. 8
  40. 30

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