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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 549 · 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 triangle ABC, angle A = 30° and angle B = 124°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  4. 4.Can a triangle have sides of 3 cm, 17 cm and 12 cm? (a) Yes (b) No
  5. 5.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 56° and angle B = 20°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 29° and 55°. What is the exterior angle (in degrees)?
  9. 9.Can a triangle have sides of 11 cm, 25 cm and 10 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 7 cm. How long is the third side (in cm)?
  11. 11.The two interior opposite angles of a triangle are 33° and 36°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 49° and angle B = 86°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 80° and 57°. What is the exterior angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 3 cm, 10 cm and 2 cm? (a) Yes (b) No
  18. 18.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  19. 19.Can a triangle have sides of 2 cm, 5 cm and 5 cm? (a) Yes (b) No
  20. 20.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 98° and angle B = 29°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 76° and angle B = 27°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 74° and 41°. What is the exterior angle (in degrees)?
  24. 24.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)?
  25. 25.Can a triangle have sides of 18 cm, 7 cm and 8 cm? (a) No (b) Yes
  26. 26.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  28. 28.Can a triangle have sides of 8 cm, 3 cm and 14 cm? (a) No (b) Yes
  29. 29.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)?
  30. 30.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 80° and 76°. What is the exterior angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  34. 34.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  36. 36.Can a triangle have sides of 20 cm, 8 cm and 11 cm? (a) Yes (b) No
  37. 37.In triangle ABC, angle A = 96° and angle B = 61°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 55° and 73°. What is the exterior angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?

Answer key

  1. 26
  2. 23
  3. 64
  4. No
  5. 40
  6. 104
  7. 12
  8. 84
  9. No
  10. 24
  11. 69
  12. 45
  13. 137
  14. 104
  15. 48
  16. 51
  17. No
  18. 26
  19. Yes
  20. 19
  21. 53
  22. 77
  23. 115
  24. 8
  25. No
  26. 75
  27. 90
  28. No
  29. 3
  30. 90
  31. 72
  32. 156
  33. 34
  34. 72
  35. 50
  36. No
  37. 23
  38. 128
  39. 50
  40. 39

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