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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 678 · 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 = 99° and angle B = 31°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 71° and 61°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 7 cm, 5 cm and 5 cm? (a) Yes (b) No
  6. 6.In triangle ABC, angle A = 58° and angle B = 23°. What is angle C (in degrees)?
  7. 7.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)?
  8. 8.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  10. 10.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)?
  11. 11.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 5 cm, 9 cm and 9 cm? (a) Yes (b) No
  14. 14.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  16. 16.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)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  18. 18.An exterior angle of a triangle is 147°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  19. 19.Can a triangle have sides of 14 cm, 7 cm and 7 cm? (a) No (b) Yes
  20. 20.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 10 cm, 11 cm and 10 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 5 cm, 16 cm and 10 cm? (a) Yes (b) No
  23. 23.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  24. 24.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 33° and 40°. What is the exterior angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 51° and 73°. What is the exterior angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 93° and angle B = 65°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 71° and 66°. What is the exterior angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  37. 37.Can a triangle have sides of 7 cm, 7 cm and 3 cm? (a) No (b) Yes
  38. 38.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 10 cm, 7 cm and 20 cm? (a) No (b) Yes

Answer key

  1. 50
  2. 34
  3. 132
  4. 65
  5. Yes
  6. 99
  7. 16
  8. 48
  9. 68
  10. 8
  11. 75
  12. 67
  13. Yes
  14. 68
  15. 70
  16. 24
  17. 79
  18. 76
  19. No
  20. 50
  21. Yes
  22. No
  23. 9
  24. 100
  25. 73
  26. 124
  27. 80
  28. 20
  29. 22
  30. 26
  31. 60
  32. 137
  33. 70
  34. 45
  35. 32
  36. 45
  37. Yes
  38. 41
  39. 10
  40. No

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