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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 527 · 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.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 38° and angle B = 43°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 97° and angle B = 46°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 6 cm, 13 cm and 5 cm? (a) Yes (b) No
  8. 8.Can a triangle have sides of 4 cm, 4 cm and 12 cm? (a) Yes (b) No
  9. 9.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  11. 11.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)?
  12. 12.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  15. 15.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)?
  16. 16.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 8 cm, 8 cm and 7 cm? (a) Yes (b) No
  19. 19.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  20. 20.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  21. 21.Can a triangle have sides of 9 cm, 7 cm and 3 cm? (a) No (b) Yes
  22. 22.Can a triangle have sides of 22 cm, 6 cm and 11 cm? (a) Yes (b) No
  23. 23.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 3 cm, 4 cm and 2 cm? (a) No (b) Yes
  25. 25.The two interior opposite angles of a triangle are 53° and 64°. What is the exterior angle (in degrees)?
  26. 26.Can a triangle have sides of 5 cm, 3 cm and 7 cm? (a) No (b) Yes
  27. 27.Can a triangle have sides of 17 cm, 9 cm and 8 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 44° and angle B = 58°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 35° and angle B = 41°. What is angle C (in degrees)?
  30. 30.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  31. 31.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  32. 32.Can a triangle have sides of 15 cm, 12 cm and 3 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 12 cm, 7 cm and 22 cm? (a) No (b) Yes
  34. 34.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 74° and angle B = 33°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 44° and 50°. What is the exterior angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  38. 38.In triangle ABC, angle A = 70° and angle B = 55°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 38° and 76°. What is the exterior angle (in degrees)?

Answer key

  1. 30
  2. 99
  3. 100
  4. 70
  5. 37
  6. 80
  7. No
  8. No
  9. 6
  10. 69
  11. 15
  12. 52
  13. 37
  14. 25
  15. 8
  16. 48
  17. 35
  18. Yes
  19. 45
  20. 44
  21. Yes
  22. No
  23. 70
  24. Yes
  25. 117
  26. Yes
  27. No
  28. 78
  29. 104
  30. 24
  31. 75
  32. No
  33. No
  34. 108
  35. 73
  36. 94
  37. 26
  38. 55
  39. 64
  40. 114

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