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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 379 · 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.In triangle ABC, angle A = 59° and angle B = 70°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 8 cm, 18 cm and 7 cm? (a) Yes (b) No
  3. 3.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 25° and angle B = 69°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  6. 6.Can a triangle have sides of 19 cm, 7 cm and 7 cm? (a) No (b) Yes
  7. 7.Can a triangle have sides of 9 cm, 6 cm and 5 cm? (a) Yes (b) No
  8. 8.Can a triangle have sides of 10 cm, 12 cm and 5 cm? (a) Yes (b) No
  9. 9.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 57° and 62°. What is the exterior angle (in degrees)?
  12. 12.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 48° and 53°. What is the exterior angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  16. 16.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 23° and 32°. What is the exterior angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  19. 19.In triangle ABC, angle A = 93° and angle B = 42°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  21. 21.Can a triangle have sides of 8 cm, 18 cm and 9 cm? (a) Yes (b) No
  22. 22.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  24. 24.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 4 cm, 5 cm and 7 cm? (a) No (b) Yes
  26. 26.In triangle ABC, angle A = 71° and angle B = 88°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 3 cm, 9 cm and 9 cm? (a) No (b) Yes
  28. 28.In triangle ABC, angle A = 63° and angle B = 31°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 36° and angle B = 29°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 4 cm, 2 cm and 4 cm? (a) No (b) Yes
  31. 31.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 85° and angle B = 31°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 4 cm, 6 cm and 8 cm? (a) No (b) Yes
  34. 34.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  35. 35.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 49° and angle B = 56°. What is angle C (in degrees)?
  37. 37.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)?
  38. 38.The two interior opposite angles of a triangle are 23° and 62°. What is the exterior angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  40. 40.Can a triangle have sides of 15 cm, 9 cm and 3 cm? (a) No (b) Yes

Answer key

  1. 51
  2. No
  3. 100
  4. 86
  5. 31
  6. No
  7. Yes
  8. Yes
  9. 84
  10. 66
  11. 119
  12. 77
  13. 20
  14. 101
  15. 70
  16. 57
  17. 55
  18. 34
  19. 45
  20. 20
  21. No
  22. 100
  23. 25
  24. 10
  25. Yes
  26. 21
  27. Yes
  28. 86
  29. 115
  30. Yes
  31. 22
  32. 64
  33. Yes
  34. 25
  35. 70
  36. 75
  37. 24
  38. 85
  39. 30
  40. No

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