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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 998 · 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 21°. What is the third angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  6. 6.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)?
  7. 7.Can a triangle have sides of 12 cm, 6 cm and 9 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 77° and angle B = 34°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 72° and 36°. What is the exterior angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 36° and 24°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  14. 14.Can a triangle have sides of 3 cm, 9 cm and 14 cm? (a) Yes (b) No
  15. 15.An exterior angle of a triangle is 119°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  19. 19.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  21. 21.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)?
  22. 22.The two interior opposite angles of a triangle are 20° and 28°. What is the exterior angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  24. 24.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  26. 26.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 34° and angle B = 103°. What is angle C (in degrees)?
  29. 29.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  30. 30.Can a triangle have sides of 8 cm, 11 cm and 8 cm? (a) Yes (b) No
  31. 31.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 39° and angle B = 64°. What is angle C (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 34° and 50°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 57° and angle B = 72°. What is angle C (in degrees)?
  36. 36.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)?
  37. 37.In triangle ABC, angle A = 93° and angle B = 28°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 64° and 48°. What is the exterior angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 49° and 65°. What is the exterior angle (in degrees)?

Answer key

  1. 69
  2. 13
  3. 22
  4. 110
  5. 90
  6. 8
  7. Yes
  8. 124
  9. 69
  10. 100
  11. 108
  12. 60
  13. 75
  14. No
  15. 56
  16. 67
  17. 90
  18. 17
  19. 77
  20. 33
  21. 15
  22. 48
  23. 17
  24. 32
  25. 18
  26. 35
  27. 34
  28. 43
  29. 20
  30. Yes
  31. 13
  32. 80
  33. 77
  34. 84
  35. 51
  36. 8
  37. 59
  38. 49
  39. 112
  40. 114

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