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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 594 · 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.Can a triangle have sides of 9 cm, 8 cm and 3 cm? (a) No (b) Yes
  2. 2.In triangle ABC, angle A = 42° and angle B = 53°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 36° and 25°. What is the exterior angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  6. 6.In triangle ABC, angle A = 33° and angle B = 66°. What is angle C (in degrees)?
  7. 7.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)?
  8. 8.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 43° and 52°. What is the exterior angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 62° and 23°. What is the exterior angle (in degrees)?
  11. 11.Can a triangle have sides of 17 cm, 5 cm and 10 cm? (a) No (b) Yes
  12. 12.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  13. 13.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  17. 17.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)?
  18. 18.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 39° and 52°. What is the exterior angle (in degrees)?
  23. 23.Can a triangle have sides of 11 cm, 7 cm and 10 cm? (a) No (b) Yes
  24. 24.In an isosceles triangle, the angle between the two equal sides is 138°. What is each of the other two angles (in degrees)?
  25. 25.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  26. 26.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  27. 27.In triangle ABC, angle A = 51° and angle B = 60°. What is angle C (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 35° and 30°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  34. 34.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)?
  35. 35.Can a triangle have sides of 6 cm, 10 cm and 19 cm? (a) Yes (b) No
  36. 36.In triangle ABC, angle A = 20° and angle B = 29°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 22 cm, 8 cm and 12 cm? (a) No (b) Yes
  38. 38.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  40. 40.The two interior opposite angles of a triangle are 49° and 29°. What is the exterior angle (in degrees)?

Answer key

  1. Yes
  2. 85
  3. 67
  4. 61
  5. 32
  6. 81
  7. 8
  8. 76
  9. 95
  10. 85
  11. No
  12. 19
  13. 52
  14. 13
  15. 120
  16. 45
  17. 7
  18. 29
  19. 48
  20. 82
  21. 72
  22. 91
  23. Yes
  24. 21
  25. 16
  26. 4
  27. 69
  28. 70
  29. 15
  30. 65
  31. 13
  32. 52
  33. 78
  34. 15
  35. No
  36. 131
  37. No
  38. 72
  39. 10
  40. 78

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