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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 474 · 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 70°. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 68° and angle B = 56°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  5. 5.Can a triangle have sides of 5 cm, 2 cm and 10 cm? (a) No (b) Yes
  6. 6.The two interior opposite angles of a triangle are 56° and 52°. What is the exterior angle (in degrees)?
  7. 7.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 10 cm, 4 cm and 9 cm? (a) No (b) Yes
  9. 9.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 78° and angle B = 33°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 62° and angle B = 42°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 12 cm, 5 cm and 5 cm? (a) Yes (b) No
  14. 14.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 30° and angle B = 30°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  17. 17.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 54° and 65°. What is the exterior angle (in degrees)?
  19. 19.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)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  21. 21.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 45° and 62°. What is the exterior angle (in degrees)?
  23. 23.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  24. 24.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  27. 27.Can a triangle have sides of 9 cm, 5 cm and 2 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 38° and angle B = 33°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 78° and 78°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  33. 33.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 25° and 54°. What is the exterior angle (in degrees)?
  35. 35.Can a triangle have sides of 11 cm, 8 cm and 21 cm? (a) Yes (b) No
  36. 36.Can a triangle have sides of 10 cm, 11 cm and 9 cm? (a) No (b) Yes
  37. 37.Can a triangle have sides of 3 cm, 3 cm and 5 cm? (a) No (b) Yes
  38. 38.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  39. 39.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 19 cm, 3 cm and 11 cm? (a) No (b) Yes

Answer key

  1. 20
  2. 46
  3. 56
  4. 17
  5. No
  6. 108
  7. 72
  8. Yes
  9. 56
  10. 74
  11. 69
  12. 76
  13. No
  14. 22
  15. 120
  16. 60
  17. 30
  18. 119
  19. 24
  20. 80
  21. 5
  22. 107
  23. 12
  24. 15
  25. 60
  26. 20
  27. No
  28. 109
  29. 156
  30. 53
  31. 128
  32. 8
  33. 126
  34. 79
  35. No
  36. Yes
  37. Yes
  38. 25
  39. 52
  40. No

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