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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 914 · 40 sums
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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.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  6. 6.In triangle ABC, angle A = 100° and angle B = 56°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  9. 9.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  11. 11.Can a triangle have sides of 3 cm, 6 cm and 13 cm? (a) Yes (b) No
  12. 12.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 61° and angle B = 21°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 14 cm, 12 cm and 2 cm? (a) Yes (b) No
  18. 18.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  19. 19.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  20. 20.In triangle ABC, angle A = 57° and angle B = 63°. What is angle C (in degrees)?
  21. 21.In triangle ABC, angle A = 62° and angle B = 45°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 20° and angle B = 92°. What is angle C (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  26. 26.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  30. 30.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 70° and 33°. What is the exterior angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 46° and 28°. What is the exterior angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 77° and angle B = 29°. What is angle C (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 a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  37. 37.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  38. 38.Can a triangle have sides of 10 cm, 7 cm and 4 cm? (a) No (b) Yes
  39. 39.The two interior opposite angles of a triangle are 21° and 71°. What is the exterior angle (in degrees)?
  40. 40.Can a triangle have sides of 4 cm, 9 cm and 12 cm? (a) Yes (b) No

Answer key

  1. 36
  2. 74
  3. 60
  4. 69
  5. 13
  6. 24
  7. 28
  8. 23
  9. 8
  10. 53
  11. No
  12. 48
  13. 40
  14. 46
  15. 98
  16. 21
  17. No
  18. 60
  19. 15
  20. 60
  21. 73
  22. 68
  23. 46
  24. 20
  25. 25
  26. 54
  27. 69
  28. 48
  29. 90
  30. 50
  31. 103
  32. 74
  33. 72
  34. 74
  35. 12
  36. 17
  37. 12
  38. Yes
  39. 92
  40. Yes

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