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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 485 · 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 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  4. 4.Can a triangle have sides of 16 cm, 7 cm and 5 cm? (a) No (b) Yes
  5. 5.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 20 cm, 9 cm and 9 cm? (a) Yes (b) No
  7. 7.The two interior opposite angles of a triangle are 42° and 23°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 8 cm, 3 cm and 7 cm? (a) Yes (b) No
  9. 9.Can a triangle have sides of 11 cm, 3 cm and 14 cm? (a) No (b) Yes
  10. 10.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)?
  11. 11.Can a triangle have sides of 5 cm, 8 cm and 9 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 56° and angle B = 83°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  16. 16.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)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 74° and 27°. What is the exterior angle (in degrees)?
  22. 22.In triangle ABC, angle A = 51° and angle B = 33°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 55° and 32°. What is the exterior angle (in degrees)?
  25. 25.Can a triangle have sides of 3 cm, 10 cm and 16 cm? (a) Yes (b) No
  26. 26.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  32. 32.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  34. 34.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)?
  35. 35.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  37. 37.Can a triangle have sides of 5 cm, 10 cm and 7 cm? (a) Yes (b) No
  38. 38.In triangle ABC, angle A = 49° and angle B = 30°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 52° and angle B = 76°. What is angle C (in degrees)?

Answer key

  1. 8
  2. 24
  3. 20
  4. No
  5. 46
  6. No
  7. 65
  8. Yes
  9. No
  10. 7
  11. Yes
  12. 41
  13. 34
  14. 22
  15. 26
  16. 15
  17. 47
  18. 73
  19. 80
  20. 19
  21. 101
  22. 96
  23. 70
  24. 87
  25. No
  26. 68
  27. 61
  28. 40
  29. 90
  30. 20
  31. 49
  32. 56
  33. 44
  34. 15
  35. 28
  36. 40
  37. Yes
  38. 101
  39. 84
  40. 52

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