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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 570 · 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 = 40° and angle B = 108°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 18 cm, 12 cm and 3 cm? (a) No (b) Yes
  5. 5.Can a triangle have sides of 7 cm, 11 cm and 18 cm? (a) No (b) Yes
  6. 6.In triangle ABC, angle A = 96° and angle B = 40°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 37° and angle B = 88°. What is angle C (in degrees)?
  8. 8.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  9. 9.Can a triangle have sides of 8 cm, 9 cm and 18 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 41° and angle B = 56°. What is angle C (in degrees)?
  11. 11.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)?
  12. 12.Can a triangle have sides of 8 cm, 8 cm and 19 cm? (a) No (b) Yes
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  16. 16.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 78° and angle B = 80°. What is angle C (in degrees)?
  18. 18.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)?
  19. 19.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 94° and angle B = 29°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  25. 25.In triangle ABC, angle A = 62° and angle B = 92°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 58° and angle B = 62°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  30. 30.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 25 cm, 9 cm and 12 cm? (a) Yes (b) No
  32. 32.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 32° and angle B = 37°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 7 cm, 13 cm and 8 cm? (a) Yes (b) No
  35. 35.Can a triangle have sides of 6 cm, 5 cm and 3 cm? (a) No (b) Yes
  36. 36.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 7 cm, 9 cm and 3 cm? (a) No (b) Yes
  38. 38.Can a triangle have sides of 8 cm, 8 cm and 20 cm? (a) Yes (b) No
  39. 39.In triangle ABC, angle A = 35° and angle B = 25°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?

Answer key

  1. 32
  2. 84
  3. 33
  4. No
  5. No
  6. 44
  7. 55
  8. 61
  9. No
  10. 83
  11. 15
  12. No
  13. 72
  14. 32
  15. 20
  16. 32
  17. 22
  18. 7
  19. 108
  20. 48
  21. 57
  22. 19
  23. 44
  24. 71
  25. 26
  26. 60
  27. 70
  28. 84
  29. 25
  30. 10
  31. No
  32. 32
  33. 111
  34. Yes
  35. Yes
  36. 38
  37. Yes
  38. No
  39. 120
  40. 51

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