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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 652 · 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 an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (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.In triangle ABC, angle A = 37° and angle B = 23°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 25° and angle B = 29°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  6. 6.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 33° and 20°. What is the exterior angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  9. 9.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  11. 11.An exterior angle of a triangle is 42°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  12. 12.Can a triangle have sides of 9 cm, 3 cm and 13 cm? (a) No (b) Yes
  13. 13.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  14. 14.Can a triangle have sides of 2 cm, 1 cm and 2 cm? (a) Yes (b) No
  15. 15.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  17. 17.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)?
  18. 18.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 44° and angle B = 27°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  21. 21.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  23. 23.In triangle ABC, angle A = 26° and angle B = 42°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 13 cm, 10 cm and 11 cm? (a) Yes (b) No
  25. 25.Can a triangle have sides of 5 cm, 9 cm and 16 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 29° and angle B = 55°. What is angle C (in degrees)?
  27. 27.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)?
  28. 28.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  30. 30.In triangle ABC, angle A = 62° and angle B = 44°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 68° and angle B = 27°. What is angle C (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 74° and 39°. What is the exterior angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  37. 37.In triangle ABC, angle A = 35° and angle B = 51°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 93° and angle B = 60°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 10 cm, 23 cm and 12 cm? (a) Yes (b) No

Answer key

  1. 19
  2. 34
  3. 120
  4. 126
  5. 18
  6. 53
  7. 53
  8. 20
  9. 70
  10. 79
  11. 20
  12. No
  13. 18
  14. Yes
  15. 90
  16. 12
  17. 7
  18. 53
  19. 109
  20. 36
  21. 21
  22. 36
  23. 112
  24. Yes
  25. No
  26. 96
  27. 24
  28. 20
  29. 64
  30. 74
  31. 85
  32. 113
  33. 76
  34. 40
  35. 12
  36. 11
  37. 94
  38. 27
  39. 68
  40. No

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