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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 706 · 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 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  2. 2.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)?
  3. 3.In triangle ABC, angle A = 74° and angle B = 34°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 7 cm, 18 cm and 8 cm? (a) No (b) Yes
  5. 5.An exterior angle of a triangle is 151°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 24° and 38°. What is the exterior angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 68° and angle B = 90°. What is angle C (in degrees)?
  12. 12.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)?
  13. 13.Can a triangle have sides of 10 cm, 10 cm and 10 cm? (a) No (b) Yes
  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 triangle ABC, angle A = 33° and angle B = 80°. What is angle C (in degrees)?
  16. 16.Can a triangle have sides of 10 cm, 3 cm and 11 cm? (a) No (b) Yes
  17. 17.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  18. 18.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  19. 19.Can a triangle have sides of 8 cm, 4 cm and 9 cm? (a) Yes (b) No
  20. 20.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)?
  21. 21.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  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.The two interior opposite angles of a triangle are 23° and 52°. What is the exterior angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (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 two interior opposite angles of a triangle are 68° and 50°. What is the exterior angle (in degrees)?
  28. 28.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  30. 30.In triangle ABC, angle A = 48° and angle B = 92°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 54° and 38°. What is the exterior angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 7 cm, 7 cm and 3 cm? (a) Yes (b) No
  36. 36.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  37. 37.Can a triangle have sides of 10 cm, 2 cm and 8 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 68° and 27°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 99° and angle B = 43°. What is angle C (in degrees)?

Answer key

  1. 15
  2. 12
  3. 72
  4. No
  5. 78
  6. 62
  7. 100
  8. 60
  9. 90
  10. 50
  11. 22
  12. 8
  13. Yes
  14. 15
  15. 67
  16. Yes
  17. 55
  18. 80
  19. Yes
  20. 7
  21. 17
  22. 24
  23. 75
  24. 80
  25. 57
  26. 68
  27. 118
  28. 73
  29. 25
  30. 40
  31. 120
  32. 92
  33. 16
  34. 134
  35. Yes
  36. 72
  37. No
  38. 48
  39. 95
  40. 38

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