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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 562 · 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.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  3. 3.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 7 cm, 20 cm and 11 cm? (a) Yes (b) No
  7. 7.An exterior angle of a triangle is 149°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 7 cm, 9 cm and 3 cm? (a) No (b) Yes
  9. 9.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 60° and angle B = 88°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  15. 15.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)?
  16. 16.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  17. 17.Can a triangle have sides of 3 cm, 11 cm and 7 cm? (a) No (b) Yes
  18. 18.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 25° and angle B = 58°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 40° and angle B = 99°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 17 cm and 7 cm? (a) Yes (b) No
  23. 23.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  24. 24.Can a triangle have sides of 10 cm, 7 cm and 22 cm? (a) Yes (b) No
  25. 25.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  26. 26.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  27. 27.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 69° and 41°. What is the exterior angle (in degrees)?
  29. 29.In triangle ABC, angle A = 84° and angle B = 33°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 9 cm, 3 cm and 13 cm? (a) Yes (b) No
  31. 31.In triangle ABC, angle A = 56° and angle B = 45°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 63° and angle B = 92°. What is angle C (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  34. 34.The two interior opposite angles of a triangle are 50° and 28°. What is the exterior angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 68° and 75°. What is the exterior angle (in degrees)?
  36. 36.In triangle ABC, angle A = 93° and angle B = 58°. What is angle C (in degrees)?
  37. 37.The longest side of a right-angled triangle is 25 cm and one of the other sides is 20 cm. How long is the third side (in cm)?
  38. 38.Can a triangle have sides of 17 cm, 12 cm and 3 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 11 cm, 9 cm and 21 cm? (a) No (b) Yes
  40. 40.In triangle ABC, angle A = 47° and angle B = 37°. What is angle C (in degrees)?

Answer key

  1. 36
  2. 17
  3. 21
  4. 10
  5. 106
  6. No
  7. 70
  8. Yes
  9. 32
  10. 10
  11. 23
  12. 32
  13. 13
  14. 57
  15. 24
  16. 40
  17. No
  18. 90
  19. 17
  20. 97
  21. 41
  22. No
  23. 31
  24. No
  25. 13
  26. 26
  27. 14
  28. 110
  29. 63
  30. No
  31. 79
  32. 25
  33. 25
  34. 78
  35. 143
  36. 29
  37. 15
  38. No
  39. No
  40. 96

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