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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 222 · 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.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  2. 2.In triangle ABC, angle A = 20° and angle B = 48°. What is angle C (in degrees)?
  3. 3.Can a triangle have sides of 23 cm, 11 cm and 8 cm? (a) No (b) Yes
  4. 4.Can a triangle have sides of 14 cm, 9 cm and 12 cm? (a) Yes (b) No
  5. 5.Can a triangle have sides of 20 cm, 12 cm and 7 cm? (a) Yes (b) No
  6. 6.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  7. 7.In triangle ABC, angle A = 61° and angle B = 67°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  9. 9.In triangle ABC, angle A = 44° and angle B = 82°. What is angle C (in degrees)?
  10. 10.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)?
  11. 11.The two interior opposite angles of a triangle are 63° and 27°. What is the exterior angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 42° and 73°. What is the exterior angle (in degrees)?
  13. 13.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  14. 14.Can a triangle have sides of 16 cm, 10 cm and 11 cm? (a) Yes (b) No
  15. 15.Can a triangle have sides of 9 cm, 12 cm and 7 cm? (a) No (b) Yes
  16. 16.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  20. 20.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  22. 22.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)?
  23. 23.In triangle ABC, angle A = 49° and angle B = 102°. What is angle C (in degrees)?
  24. 24.In triangle ABC, angle A = 60° and angle B = 28°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  28. 28.The two interior opposite angles of a triangle are 21° and 64°. What is the exterior angle (in degrees)?
  29. 29.In triangle ABC, angle A = 80° and angle B = 50°. What is angle C (in degrees)?
  30. 30.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  34. 34.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 67°. What is the other one (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.The two interior opposite angles of a triangle are 59° and 34°. What is the exterior angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 16 cm, 12 cm and 3 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 9 cm, 1 cm and 9 cm? (a) No (b) Yes
  40. 40.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?

Answer key

  1. 46
  2. 112
  3. No
  4. Yes
  5. No
  6. 25
  7. 52
  8. 34
  9. 54
  10. 8
  11. 90
  12. 115
  13. 55
  14. Yes
  15. Yes
  16. 69
  17. 40
  18. 23
  19. 57
  20. 36
  21. 20
  22. 24
  23. 29
  24. 92
  25. 55
  26. 68
  27. 6
  28. 85
  29. 50
  30. 5
  31. 60
  32. 49
  33. 72
  34. 74
  35. 17
  36. 93
  37. 80
  38. No
  39. Yes
  40. 38

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