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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 508 · 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 two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  2. 2.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  6. 6.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 73° and 46°. What is the exterior angle (in degrees)?
  11. 11.In triangle ABC, angle A = 47° and angle B = 64°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 84° and angle B = 56°. What is angle C (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 41° and 31°. What is the exterior angle (in degrees)?
  14. 14.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 58° and angle B = 24°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 92° and angle B = 57°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 64° and 37°. What is the exterior angle (in degrees)?
  19. 19.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)?
  20. 20.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  22. 22.Can a triangle have sides of 11 cm, 6 cm and 14 cm? (a) No (b) Yes
  23. 23.Can a triangle have sides of 2 cm, 3 cm and 5 cm? (a) No (b) Yes
  24. 24.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  26. 26.In triangle ABC, angle A = 92° and angle B = 32°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 62° and angle B = 39°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 24 cm, 10 cm and 10 cm? (a) Yes (b) No
  29. 29.Can a triangle have sides of 10 cm, 7 cm and 12 cm? (a) No (b) Yes
  30. 30.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  32. 32.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  33. 33.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  36. 36.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 60° and 57°. What is the exterior angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 34° and 35°. What is the exterior angle (in degrees)?
  40. 40.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?

Answer key

  1. 5
  2. 44
  3. 30
  4. 24
  5. 15
  6. 80
  7. 18
  8. 80
  9. 110
  10. 119
  11. 69
  12. 40
  13. 72
  14. 30
  15. 98
  16. 84
  17. 31
  18. 101
  19. 7
  20. 26
  21. 20
  22. Yes
  23. No
  24. 47
  25. 39
  26. 56
  27. 79
  28. No
  29. Yes
  30. 59
  31. 20
  32. 45
  33. 34
  34. 34
  35. 26
  36. 23
  37. 117
  38. 43
  39. 69
  40. 54

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