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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 502 · 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 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)?
  2. 2.In triangle ABC, angle A = 27° and angle B = 88°. What is angle C (in degrees)?
  3. 3.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)?
  4. 4.In triangle ABC, angle A = 27° and angle B = 85°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  6. 6.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)?
  7. 7.The two interior opposite angles of a triangle are 72° and 69°. What is the exterior angle (in degrees)?
  8. 8.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)?
  9. 9.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 5 cm, 6 cm and 7 cm? (a) No (b) Yes
  11. 11.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  12. 12.In triangle ABC, angle A = 80° and angle B = 45°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  14. 14.In triangle ABC, angle A = 68° and angle B = 52°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 64° and angle B = 92°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 8 cm, 2 cm and 9 cm? (a) Yes (b) No
  18. 18.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  19. 19.Can a triangle have sides of 7 cm, 17 cm and 7 cm? (a) Yes (b) No
  20. 20.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 99° and angle B = 22°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  23. 23.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 89° and angle B = 22°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 22° and 52°. What is the exterior angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  30. 30.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)?
  31. 31.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  35. 35.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)?
  36. 36.In triangle ABC, angle A = 70° and angle B = 49°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 80° and angle B = 70°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 7 cm, 10 cm and 22 cm? (a) Yes (b) No
  39. 39.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?

Answer key

  1. 24
  2. 65
  3. 24
  4. 68
  5. 69
  6. 15
  7. 141
  8. 8
  9. 21
  10. Yes
  11. 49
  12. 55
  13. 17
  14. 60
  15. 36
  16. 24
  17. Yes
  18. 24
  19. No
  20. 90
  21. 59
  22. 75
  23. 100
  24. 26
  25. 69
  26. 16
  27. 56
  28. 74
  29. 20
  30. 36
  31. 60
  32. 44
  33. 40
  34. 17
  35. 15
  36. 61
  37. 30
  38. No
  39. 50
  40. 75

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