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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 984 · 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 24 cm. How long is the third side (in cm)?
  2. 2.Can a triangle have sides of 7 cm, 7 cm and 6 cm? (a) No (b) Yes
  3. 3.Can a triangle have sides of 4 cm, 2 cm and 4 cm? (a) No (b) Yes
  4. 4.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 32° and angle B = 75°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 55° each. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  9. 9.In triangle ABC, angle A = 95° and angle B = 23°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 9 cm, 12 cm and 9 cm? (a) Yes (b) No
  14. 14.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 4 cm, 6 cm and 6 cm? (a) No (b) Yes
  16. 16.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  17. 17.In triangle ABC, angle A = 34° and angle B = 82°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 50° and 68°. What is the exterior angle (in degrees)?
  20. 20.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 7 cm, 3 cm and 5 cm? (a) Yes (b) No
  23. 23.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  24. 24.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  25. 25.In triangle ABC, angle A = 45° and angle B = 112°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 4 cm, 6 cm and 7 cm? (a) No (b) Yes
  28. 28.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 77° and angle B = 51°. What is angle C (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 12 cm, 25 cm and 10 cm? (a) No (b) Yes
  33. 33.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 4 cm, 14 cm and 6 cm? (a) Yes (b) No
  36. 36.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  37. 37.The two interior opposite angles of a triangle are 32° and 27°. What is the exterior angle (in degrees)?
  38. 38.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)?
  39. 39.In triangle ABC, angle A = 77° and angle B = 78°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?

Answer key

  1. 7
  2. Yes
  3. Yes
  4. 55
  5. 13
  6. 73
  7. 70
  8. 35
  9. 62
  10. 35
  11. 19
  12. 57
  13. Yes
  14. 66
  15. Yes
  16. 18
  17. 64
  18. 11
  19. 118
  20. 66
  21. 78
  22. Yes
  23. 90
  24. 46
  25. 23
  26. 75
  27. Yes
  28. 36
  29. 52
  30. 15
  31. 43
  32. No
  33. 72
  34. 63
  35. No
  36. 39
  37. 59
  38. 8
  39. 25
  40. 32

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