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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 580 · 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 12 cm, 16 cm and 4 cm? (a) No (b) Yes
  2. 2.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)?
  3. 3.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  5. 5.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)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  7. 7.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)?
  8. 8.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  10. 10.Can a triangle have sides of 7 cm, 8 cm and 16 cm? (a) Yes (b) No
  11. 11.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 23° and 63°. What is the exterior angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  14. 14.Can a triangle have sides of 10 cm, 5 cm and 8 cm? (a) No (b) Yes
  15. 15.The two interior opposite angles of a triangle are 29° and 70°. What is the exterior angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 67° and 67°. What is the exterior angle (in degrees)?
  18. 18.In triangle ABC, angle A = 39° and angle B = 101°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 74° and 21°. What is the exterior angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 77° and 78°. What is the exterior angle (in degrees)?
  23. 23.Can a triangle have sides of 6 cm, 6 cm and 3 cm? (a) Yes (b) No
  24. 24.Can a triangle have sides of 5 cm, 2 cm and 10 cm? (a) No (b) Yes
  25. 25.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  33. 33.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)?
  34. 34.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  35. 35.Can a triangle have sides of 15 cm, 2 cm and 9 cm? (a) Yes (b) No
  36. 36.Can a triangle have sides of 5 cm, 8 cm and 16 cm? (a) Yes (b) No
  37. 37.In triangle ABC, angle A = 70° and angle B = 62°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 11 cm, 24 cm and 10 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 4 cm, 2 cm and 3 cm? (a) No (b) Yes
  40. 40.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?

Answer key

  1. No
  2. 4
  3. 74
  4. 17
  5. 8
  6. 36
  7. 15
  8. 100
  9. 25
  10. No
  11. 45
  12. 86
  13. 45
  14. Yes
  15. 99
  16. 47
  17. 134
  18. 40
  19. 50
  20. 95
  21. 71
  22. 155
  23. Yes
  24. No
  25. 48
  26. 66
  27. 90
  28. 14
  29. 62
  30. 72
  31. 20
  32. 10
  33. 7
  34. 17
  35. No
  36. No
  37. 48
  38. No
  39. Yes
  40. 38

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