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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 963 · 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 a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 82° and angle B = 62°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  6. 6.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)?
  7. 7.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  8. 8.In triangle ABC, angle A = 52° and angle B = 27°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 3 cm, 6 cm and 3 cm? (a) No (b) Yes
  10. 10.In triangle ABC, angle A = 73° and angle B = 82°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 39° and angle B = 57°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 98° and angle B = 27°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  16. 16.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  17. 17.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  18. 18.In triangle ABC, angle A = 60° and angle B = 34°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 10 cm, 23 cm and 8 cm? (a) Yes (b) No
  20. 20.Can a triangle have sides of 2 cm, 6 cm and 7 cm? (a) Yes (b) No
  21. 21.Can a triangle have sides of 6 cm, 6 cm and 5 cm? (a) Yes (b) No
  22. 22.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  24. 24.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  25. 25.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 94° and angle B = 47°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 86° and angle B = 42°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 10 cm, 2 cm and 10 cm? (a) Yes (b) No
  36. 36.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)?
  37. 37.Can a triangle have sides of 5 cm, 7 cm and 3 cm? (a) No (b) Yes
  38. 38.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  39. 39.Can a triangle have sides of 6 cm, 10 cm and 17 cm? (a) Yes (b) No
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?

Answer key

  1. 14
  2. 36
  3. 36
  4. 45
  5. 48
  6. 7
  7. 17
  8. 101
  9. No
  10. 25
  11. 84
  12. 116
  13. 55
  14. 62
  15. 90
  16. 10
  17. 76
  18. 86
  19. No
  20. Yes
  21. Yes
  22. 48
  23. 13
  24. 10
  25. 20
  26. 80
  27. 71
  28. 12
  29. 5
  30. 90
  31. 57
  32. 39
  33. 52
  34. 59
  35. Yes
  36. 15
  37. Yes
  38. 50
  39. No
  40. 36

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