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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 144 · 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 74°. What is each of the other two angles (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 44° and 25°. 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.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 20° and angle B = 36°. What is angle C (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  8. 8.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  14. 14.In triangle ABC, angle A = 27° and angle B = 34°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 9 cm, 3 cm and 16 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  18. 18.Can a triangle have sides of 11 cm, 3 cm and 10 cm? (a) No (b) Yes
  19. 19.Can a triangle have sides of 12 cm, 13 cm and 4 cm? (a) No (b) Yes
  20. 20.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 12 cm, 13 cm and 2 cm? (a) Yes (b) No
  25. 25.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 7 cm, 14 cm and 6 cm? (a) No (b) Yes
  28. 28.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 26° and 25°. What is the exterior angle (in degrees)?
  33. 33.Can a triangle have sides of 5 cm, 14 cm and 5 cm? (a) Yes (b) No
  34. 34.In triangle ABC, angle A = 72° and angle B = 70°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 72°. What is each of the other two angles (in degrees)?
  37. 37.Can a triangle have sides of 10 cm, 6 cm and 21 cm? (a) No (b) Yes
  38. 38.In triangle ABC, angle A = 43° and angle B = 77°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  40. 40.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)?

Answer key

  1. 53
  2. 50
  3. 69
  4. 65
  5. 33
  6. 124
  7. 13
  8. 43
  9. 42
  10. 72
  11. 36
  12. 45
  13. 43
  14. 119
  15. No
  16. 16
  17. 40
  18. Yes
  19. Yes
  20. 54
  21. 66
  22. 21
  23. 24
  24. Yes
  25. 64
  26. 134
  27. No
  28. 10
  29. 20
  30. 64
  31. 100
  32. 51
  33. No
  34. 38
  35. 70
  36. 54
  37. No
  38. 60
  39. 70
  40. 8

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