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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 130 · 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.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 6 cm and 4 cm? (a) Yes (b) No
  3. 3.The two interior opposite angles of a triangle are 65° and 31°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 100° and angle B = 41°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  6. 6.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  7. 7.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 8 cm, 7 cm and 20 cm? (a) No (b) Yes
  9. 9.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 19 cm and 10 cm? (a) No (b) Yes
  11. 11.Can a triangle have sides of 6 cm, 5 cm and 8 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 86° and angle B = 63°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  15. 15.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 52° and 46°. What is the exterior angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 20° and 20°. What is the exterior angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  19. 19.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  21. 21.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  24. 24.Can a triangle have sides of 12 cm, 4 cm and 20 cm? (a) No (b) Yes
  25. 25.In triangle ABC, angle A = 95° and angle B = 22°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 10 cm, 12 cm and 22 cm? (a) Yes (b) No
  27. 27.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 29° and angle B = 32°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 4 cm, 10 cm and 11 cm? (a) No (b) Yes
  30. 30.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  32. 32.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)?
  33. 33.Can a triangle have sides of 10 cm, 3 cm and 6 cm? (a) No (b) Yes
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 23° and 35°. What is the exterior angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 20° and 76°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 37° and angle B = 29°. What is angle C (in degrees)?
  38. 38.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  39. 39.In triangle ABC, angle A = 36° and angle B = 69°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 23 cm, 10 cm and 10 cm? (a) No (b) Yes

Answer key

  1. 22
  2. Yes
  3. 96
  4. 39
  5. 51
  6. 29
  7. 24
  8. No
  9. 72
  10. Yes
  11. Yes
  12. 31
  13. 30
  14. 12
  15. 72
  16. 98
  17. 40
  18. 39
  19. 90
  20. 17
  21. 76
  22. 73
  23. 64
  24. No
  25. 63
  26. No
  27. 100
  28. 119
  29. Yes
  30. 11
  31. 15
  32. 8
  33. No
  34. 90
  35. 58
  36. 96
  37. 114
  38. 24
  39. 75
  40. No

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