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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 140 · 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 two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  2. 2.The two interior opposite angles of a triangle are 29° and 46°. What is the exterior angle (in degrees)?
  3. 3.Can a triangle have sides of 10 cm, 6 cm and 5 cm? (a) No (b) Yes
  4. 4.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  6. 6.Can a triangle have sides of 13 cm, 7 cm and 6 cm? (a) Yes (b) No
  7. 7.Can a triangle have sides of 10 cm, 11 cm and 4 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 55° and angle B = 101°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 20° and 61°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 2 cm, 8 cm and 7 cm? (a) No (b) Yes
  18. 18.In triangle ABC, angle A = 39° and angle B = 92°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 30° and angle B = 71°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 45° and angle B = 74°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 4 cm, 16 cm and 8 cm? (a) No (b) Yes
  22. 22.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  23. 23.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)?
  24. 24.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  26. 26.Can a triangle have sides of 9 cm, 7 cm and 3 cm? (a) No (b) Yes
  27. 27.In triangle ABC, angle A = 99° and angle B = 58°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 73° and 31°. What is the exterior angle (in degrees)?
  29. 29.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)?
  30. 30.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 146°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 35° and 63°. What is the exterior angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  35. 35.In triangle ABC, angle A = 27° and angle B = 92°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 25° and angle B = 65°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 98° and angle B = 60°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 27° and angle B = 69°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?

Answer key

  1. 26
  2. 75
  3. Yes
  4. 40
  5. 5
  6. No
  7. Yes
  8. 102
  9. 22
  10. 24
  11. 78
  12. 81
  13. 70
  14. 24
  15. 32
  16. 62
  17. Yes
  18. 49
  19. 79
  20. 61
  21. No
  22. 44
  23. 12
  24. 90
  25. 90
  26. Yes
  27. 23
  28. 104
  29. 8
  30. 20
  31. 74
  32. 66
  33. 98
  34. 13
  35. 61
  36. 90
  37. 22
  38. 84
  39. 120
  40. 122

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