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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 150 · 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 10 cm and 24 cm. How long is the longest side (in cm)?
  2. 2.Can a triangle have sides of 2 cm, 4 cm and 4 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 55° and angle B = 46°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 66° and angle B = 79°. What is angle C (in degrees)?
  5. 5.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)?
  6. 6.In triangle ABC, angle A = 94° and angle B = 23°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 35° and angle B = 56°. What is angle C (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 18 cm and 2 cm? (a) Yes (b) No
  11. 11.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  12. 12.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)?
  13. 13.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  14. 14.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  15. 15.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 38° and angle B = 72°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 47° and 40°. What is the exterior angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 11 cm, 10 cm and 24 cm? (a) No (b) Yes
  22. 22.In triangle ABC, angle A = 78° and angle B = 55°. What is angle C (in degrees)?
  23. 23.In triangle ABC, angle A = 69° and angle B = 53°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  26. 26.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  28. 28.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  30. 30.Can a triangle have sides of 22 cm, 8 cm and 9 cm? (a) Yes (b) No
  31. 31.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  32. 32.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  34. 34.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)?
  35. 35.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 85° and angle B = 23°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 3 cm, 10 cm and 3 cm? (a) No (b) Yes
  38. 38.The two interior opposite angles of a triangle are 57° and 24°. What is the exterior angle (in degrees)?
  39. 39.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)?
  40. 40.Can a triangle have sides of 3 cm, 3 cm and 4 cm? (a) Yes (b) No

Answer key

  1. 26
  2. Yes
  3. 79
  4. 35
  5. 24
  6. 63
  7. 89
  8. 75
  9. 90
  10. No
  11. 30
  12. 36
  13. 62
  14. 15
  15. 42
  16. 78
  17. 70
  18. 140
  19. 87
  20. 18
  21. No
  22. 47
  23. 58
  24. 41
  25. 66
  26. 24
  27. 27
  28. 70
  29. 122
  30. No
  31. 46
  32. 28
  33. 42
  34. 8
  35. 84
  36. 72
  37. No
  38. 81
  39. 15
  40. Yes

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