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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 665 · 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 88°. What is each of the other two angles (in degrees)?
  2. 2.Can a triangle have sides of 2 cm, 3 cm and 2 cm? (a) Yes (b) No
  3. 3.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  5. 5.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 80° and 23°. What is the exterior angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 76° and 43°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 6 cm, 11 cm and 9 cm? (a) No (b) Yes
  9. 9.Can a triangle have sides of 11 cm, 8 cm and 11 cm? (a) No (b) Yes
  10. 10.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  11. 11.Can a triangle have sides of 7 cm, 16 cm and 6 cm? (a) Yes (b) No
  12. 12.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  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.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  15. 15.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  16. 16.Can a triangle have sides of 3 cm, 9 cm and 9 cm? (a) Yes (b) No
  17. 17.In triangle ABC, angle A = 30° and angle B = 103°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 9 cm, 2 cm and 9 cm? (a) Yes (b) No
  19. 19.Can a triangle have sides of 10 cm, 8 cm and 4 cm? (a) Yes (b) No
  20. 20.In triangle ABC, angle A = 24° and angle B = 48°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 55° and angle B = 49°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 53° and angle B = 97°. What is angle C (in degrees)?
  24. 24.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  25. 25.In triangle ABC, angle A = 100° and angle B = 40°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 7 cm, 5 cm and 6 cm? (a) No (b) Yes
  27. 27.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  29. 29.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  30. 30.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 3 cm, 8 cm and 3 cm? (a) Yes (b) No
  33. 33.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 20° and 67°. What is the exterior angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  36. 36.Can a triangle have sides of 3 cm, 2 cm and 9 cm? (a) No (b) Yes
  37. 37.Can a triangle have sides of 11 cm, 14 cm and 10 cm? (a) No (b) Yes
  38. 38.In triangle ABC, angle A = 31° and angle B = 21°. What is angle C (in degrees)?
  39. 39.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)?
  40. 40.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?

Answer key

  1. 46
  2. Yes
  3. 72
  4. 25
  5. 54
  6. 103
  7. 119
  8. Yes
  9. Yes
  10. 70
  11. No
  12. 72
  13. 17
  14. 100
  15. 30
  16. Yes
  17. 47
  18. Yes
  19. Yes
  20. 108
  21. 40
  22. 76
  23. 30
  24. 28
  25. 40
  26. Yes
  27. 82
  28. 24
  29. 70
  30. 27
  31. 138
  32. No
  33. 41
  34. 87
  35. 17
  36. No
  37. Yes
  38. 128
  39. 9
  40. 12

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