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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 188 · 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 angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 10 cm, 6 cm and 5 cm? (a) No (b) Yes
  4. 4.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 9 cm, 16 cm and 7 cm? (a) Yes (b) No
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  9. 9.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)?
  10. 10.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  12. 12.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)?
  13. 13.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  15. 15.Can a triangle have sides of 4 cm, 11 cm and 20 cm? (a) No (b) Yes
  16. 16.The two interior opposite angles of a triangle are 63° and 41°. What is the exterior 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.Can a triangle have sides of 9 cm, 9 cm and 22 cm? (a) Yes (b) No
  19. 19.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 7 cm, 9 cm and 5 cm? (a) Yes (b) No
  21. 21.Can a triangle have sides of 7 cm, 12 cm and 3 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 9 cm, 11 cm and 3 cm? (a) Yes (b) No
  23. 23.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 8 cm, 6 cm and 8 cm? (a) Yes (b) No
  25. 25.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  26. 26.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  27. 27.In an isosceles triangle, the two equal angles are 63° each. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 27° and 43°. What is the exterior angle (in degrees)?
  30. 30.Can a triangle have sides of 9 cm, 7 cm and 8 cm? (a) No (b) Yes
  31. 31.Can a triangle have sides of 9 cm, 7 cm and 3 cm? (a) No (b) Yes
  32. 32.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  34. 34.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  35. 35.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 19 cm, 11 cm and 5 cm? (a) No (b) Yes
  37. 37.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 9 cm, 9 cm and 9 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 8 cm. How long is the third side (in cm)?
  40. 40.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?

Answer key

  1. 45
  2. 28
  3. Yes
  4. 72
  5. 38
  6. No
  7. 80
  8. 20
  9. 10
  10. 84
  11. 21
  12. 7
  13. 90
  14. 72
  15. No
  16. 104
  17. 50
  18. No
  19. 74
  20. Yes
  21. No
  22. Yes
  23. 140
  24. Yes
  25. 11
  26. 5
  27. 54
  28. 74
  29. 70
  30. Yes
  31. Yes
  32. 25
  33. 20
  34. 3
  35. 96
  36. No
  37. 78
  38. Yes
  39. 15
  40. 46

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