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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 516 · 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 12 cm and 5 cm. How long is the longest side (in cm)?
  2. 2.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  3. 3.Can a triangle have sides of 3 cm, 5 cm and 8 cm? (a) No (b) Yes
  4. 4.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)?
  5. 5.In triangle ABC, angle A = 33° and angle B = 98°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (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.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 12 cm, 16 cm and 3 cm? (a) Yes (b) No
  10. 10.Can a triangle have sides of 12 cm, 7 cm and 9 cm? (a) No (b) Yes
  11. 11.In triangle ABC, angle A = 65° and angle B = 28°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 6 cm, 10 cm and 9 cm? (a) No (b) Yes
  13. 13.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  14. 14.Can a triangle have sides of 4 cm, 11 cm and 7 cm? (a) No (b) Yes
  15. 15.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  16. 16.Can a triangle have sides of 12 cm, 10 cm and 5 cm? (a) No (b) Yes
  17. 17.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  18. 18.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  19. 19.The two interior opposite angles of a triangle are 44° and 29°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 34° and angle B = 96°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  22. 22.In triangle ABC, angle A = 59° and angle B = 96°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 66° and angle B = 71°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  25. 25.Can a triangle have sides of 6 cm, 3 cm and 8 cm? (a) No (b) Yes
  26. 26.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  27. 27.In triangle ABC, angle A = 24° and angle B = 87°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 43° and 31°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 2 cm, 4 cm and 2 cm? (a) Yes (b) No
  32. 32.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 38° and 55°. What is the exterior angle (in degrees)?
  34. 34.In triangle ABC, angle A = 81° and angle B = 65°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 35° and 78°. What is the exterior angle (in degrees)?
  36. 36.In triangle ABC, angle A = 25° and angle B = 128°. What is angle C (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 37° and angle B = 46°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  40. 40.In triangle ABC, angle A = 95° and angle B = 57°. What is angle C (in degrees)?

Answer key

  1. 13
  2. 36
  3. No
  4. 7
  5. 49
  6. 120
  7. 12
  8. 64
  9. No
  10. Yes
  11. 87
  12. Yes
  13. 17
  14. No
  15. 54
  16. Yes
  17. 64
  18. 16
  19. 73
  20. 50
  21. 62
  22. 25
  23. 43
  24. 50
  25. Yes
  26. 70
  27. 69
  28. 32
  29. 78
  30. 74
  31. No
  32. 63
  33. 93
  34. 34
  35. 113
  36. 27
  37. 80
  38. 97
  39. 41
  40. 28

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